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<title>What is free software? - GNU Project - Free Software Foundation (FSF)</title> |
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<h2>What is free software?</h2> |
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|
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<h3>The Free Software Definition</h3> |
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|
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<blockquote> |
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<p> |
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The free software definition presents the criteria for whether a |
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particular software program qualifies as free software. From time to |
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time we revise this definition, to clarify it or to resolve questions |
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about subtle issues. See the <a href="#History">History section</a> |
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below for a list of changes that affect the definition of free |
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software. |
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</p> |
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</blockquote> |
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|
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<p> |
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“Free software” means software that respects users' |
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freedom and community. Roughly, <b>the users have the freedom to run, |
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copy, distribute, study, change and improve the software</b>. With these |
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freedoms, the users (both individually and collectively) control the |
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program and what it does for them. |
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</p> |
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|
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<p> |
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When users don't control the program, the program controls the users. |
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The developer controls the program, and through it controls the users. |
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This nonfree or “proprietary” program is therefore an |
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instrument of unjust power. |
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</p> |
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|
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<p> |
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Thus, “free software” is a matter of liberty, not price. |
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To understand the concept, you should think of “free” as |
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in “free speech,” not as in “free beer”. |
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</p> |
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|
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<p> |
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A program is free software if the program's users have the |
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four essential freedoms: |
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</p> |
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|
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<ul> |
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<li>The freedom to run the program, for any purpose (freedom 0).</li> |
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<li>The freedom to study how the program works, and change it so it |
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does your computing as you wish (freedom 1). Access to the source |
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code is a precondition for this. |
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</li> |
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<li>The freedom to redistribute copies so you can help your neighbor |
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(freedom 2). |
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</li> |
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<li>The freedom to distribute copies of your modified versions |
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to others (freedom 3). By doing this you can give the whole |
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community a chance to benefit from your changes. |
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Access to the source code is a precondition for this. |
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</li> |
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</ul> |
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|
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<p> |
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A program is free software if users have all of these freedoms. Thus, |
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you should be free to redistribute copies, either with or without |
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modifications, either gratis or charging a fee for distribution, to |
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<a href="#exportcontrol">anyone anywhere</a>. Being free to do these |
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things means (among other things) that you do not have to ask or pay |
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for permission to do so. |
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</p> |
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|
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<p> |
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You should also have the freedom to make modifications and use them |
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privately in your own work or play, without even mentioning that they |
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exist. If you do publish your changes, you should not be required to |
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notify anyone in particular, or in any particular way. |
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</p> |
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|
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<p> |
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The freedom to run the program means the freedom for any kind of person |
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or organization to use it on any kind of computer system, for any kind of |
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overall job and purpose, without being required to communicate about it |
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with the developer or any other specific entity. In this freedom, it is |
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the <em>user's</em> purpose that matters, not the <em>developer's</em> |
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purpose; you as a user are free to run the program for your purposes, |
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and if you distribute it to someone else, she is then free to run it |
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for her purposes, but you are not entitled to impose your purposes on her. |
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</p> |
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|
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<p> |
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The freedom to redistribute copies must include binary or executable |
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forms of the program, as well as source code, for both modified and |
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unmodified versions. (Distributing programs in runnable form is necessary |
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for conveniently installable free operating systems.) It is OK if there |
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is no way to produce a binary or executable form for a certain program |
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(since some languages don't support that feature), but you must have the |
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freedom to redistribute such forms should you find or develop a way to |
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make them. |
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</p> |
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|
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<p> |
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In order for freedoms 1 and 3 (the freedom to make changes and the |
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freedom to publish the changed versions) to be meaningful, you must have |
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access to the source code of the program. Therefore, accessibility of |
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source code is a necessary condition for free software. Obfuscated |
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“source code” is not real source code and does not count |
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as source code. |
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</p> |
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|
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<p> |
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Freedom 1 includes the freedom to use your changed version in place of |
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the original. If the program is delivered in a product designed to |
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run someone else's modified versions but refuse to run yours — a |
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practice known as “tivoization” or “lockdown”, |
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or (in its practitioners' perverse terminology) as “secure |
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boot” — freedom 1 becomes a theoretical fiction rather |
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than a practical freedom. This is not sufficient. In other words, |
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these binaries are not free software even if the source code they are |
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compiled from is free. |
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</p> |
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|
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<p> |
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One important way to modify a program is by merging in available free |
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subroutines and modules. If the program's license says that you |
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cannot merge in a suitably licensed existing module — for instance, if it |
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requires you to be the copyright holder of any code you add — then the |
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license is too restrictive to qualify as free. |
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</p> |
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|
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<p> |
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Freedom 3 includes the freedom to release your modified versions |
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as free software. A free license may also permit other ways of |
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releasing them; in other words, it does not have to be |
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a <a href="/copyleft/copyleft.html">copyleft</a> license. However, a |
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license that requires modified versions to be nonfree does not qualify |
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as a free license. |
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</p> |
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|
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<p> |
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In order for these freedoms to be real, they must be permanent and |
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irrevocable as long as you do nothing wrong; if the developer of the |
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software has the power to revoke the license, or retroactively add |
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restrictions to its terms, without your doing anything wrong to give |
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cause, the software is not free. |
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</p> |
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|
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<p> |
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However, certain kinds of rules about the manner of distributing free |
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software are acceptable, when they don't conflict with the central |
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freedoms. For example, copyleft (very simply stated) is the rule that |
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when redistributing the program, you cannot add restrictions to deny |
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other people the central freedoms. This rule does not conflict with |
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the central freedoms; rather it protects them. |
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</p> |
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|
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<p> |
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“Free software” does not mean “noncommercial”. A free |
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program must be available for commercial use, commercial development, |
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and commercial distribution. Commercial development of free software |
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is no longer unusual; such free commercial software is very important. |
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You may have paid money to get copies of free software, or you may have |
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obtained copies at no charge. But regardless of how you got your copies, |
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you always have the freedom to copy and change the software, even to |
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<a href="/philosophy/selling.html">sell copies</a>. |
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</p> |
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|
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<p> |
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Whether a change constitutes an improvement is a subjective matter. |
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If your right to modify a program is limited, in substance, to changes that |
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someone else considers an improvement, that program is not free. |
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</p> |
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|
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<p> |
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However, rules about how to package a modified version are acceptable, |
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if they don't substantively limit your freedom to release modified |
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versions, or your freedom to make and use modified versions privately. |
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Thus, it is acceptable for the license to require that you change the |
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name of the modified version, remove a logo, or identify your |
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modifications as yours. As long as these requirements are not so |
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burdensome that they effectively hamper you from releasing your |
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changes, they are acceptable; you're already making other changes to |
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the program, so you won't have trouble making a few more. |
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</p> |
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|
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<p> |
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A special issue arises when a license requires changing the name by |
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which the program will be invoked from other programs. That |
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effectively hampers you from releasing your changed version so that it |
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can replace the original when invoked by those other programs. This |
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sort of requirement is acceptable only if there's a suitable aliasing |
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facility that allows you to specify the original program's name as an |
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alias for the modified version.</p> |
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|
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<p> |
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Rules that “if you make your version available in this way, you |
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must make it available in that way also” can be acceptable too, |
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on the same condition. An example of such an acceptable rule is one |
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saying that if you have distributed a |
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modified version and a previous developer asks for a copy of it, you |
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must send one. (Note that such a rule still leaves you the choice of |
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whether to distribute your version at all.) Rules that require release |
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of source code to the users for versions that you put into public use |
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are also acceptable. |
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</p> |
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|
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<p> |
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In the GNU project, we use |
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<a href="/copyleft/copyleft.html">copyleft</a> |
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to protect these freedoms legally for everyone. But |
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<a href="/philosophy/categories.html#Non-CopyleftedFreeSoftware">noncopylefted |
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free software</a> also exists. We believe there are important reasons why |
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<a href="/philosophy/pragmatic.html">it is better to use copyleft</a>, |
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but if your program is noncopylefted free software, it is still basically |
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ethical. (See <a href="/philosophy/categories.html">Categories of Free Software</a> for a description of how “free software,” “copylefted software” and other categories of software relate to each other.) |
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</p> |
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|
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<p> |
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Sometimes government <a id="exportcontrol">export control regulations</a> |
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and trade sanctions can constrain your freedom to distribute copies of |
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programs internationally. Software developers do not have the power to |
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eliminate or override these restrictions, but what they can and must do |
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is refuse to impose them as conditions of use of the program. In this |
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way, the restrictions will not affect activities and people outside the |
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jurisdictions of these governments. Thus, free software licenses |
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must not require obedience to any export regulations as a condition of |
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any of the essential freedoms. |
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</p> |
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|
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<p> |
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Most free software licenses are based on copyright, and there are limits |
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on what kinds of requirements can be imposed through copyright. If a |
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copyright-based license respects freedom in the ways described above, it |
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is unlikely to have some other sort of problem that we never anticipated |
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(though this does happen occasionally). However, some free software |
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licenses are based on contracts, and contracts can impose a much larger |
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range of possible restrictions. That means there are many possible ways |
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such a license could be unacceptably restrictive and nonfree. |
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</p> |
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|
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<p> |
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We can't possibly list all the ways that might happen. If a |
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contract-based license restricts the user in an unusual way that |
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copyright-based licenses cannot, and which isn't mentioned here as |
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legitimate, we will have to think about it, and we will probably conclude |
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it is nonfree. |
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</p> |
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|
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<p> |
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When talking about free software, it is best to avoid using terms |
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like “give away” or “for free,” because those terms imply that |
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the issue is about price, not freedom. Some common terms such |
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as “piracy” embody opinions we hope you won't endorse. See |
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<a href="/philosophy/words-to-avoid.html">Confusing Words and Phrases that |
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are Worth Avoiding</a> for a discussion of these terms. We also have |
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a list of proper <a href="/philosophy/fs-translations.html">translations of |
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“free software”</a> into various languages. |
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</p> |
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|
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<p> |
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Finally, note that criteria such as those stated in this free software |
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definition require careful thought for their interpretation. To decide |
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whether a specific software license qualifies as a free software license, |
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we judge it based on these criteria to determine whether it fits their |
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spirit as well as the precise words. If a license includes unconscionable |
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restrictions, we reject it, even if we did not anticipate the issue |
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in these criteria. Sometimes a license requirement raises an issue |
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that calls for extensive thought, including discussions with a lawyer, |
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before we can decide if the requirement is acceptable. When we reach |
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a conclusion about a new issue, we often update these criteria to make |
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it easier to see why certain licenses do or don't qualify. |
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</p> |
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|
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<p> |
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If you are interested in whether a specific license qualifies as a free |
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software license, see our <a href="/licenses/license-list.html">list |
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of licenses</a>. If the license you are concerned with is not |
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listed there, you can ask us about it by sending us email at |
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<a href="mailto:licensing@gnu.org"><licensing@gnu.org></a>. |
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</p> |
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|
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<p> |
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If you are contemplating writing a new license, please contact the |
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Free Software Foundation first by writing to that address. The |
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proliferation of different free software licenses means increased work |
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for users in understanding the licenses; we may be able to help you |
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find an existing free software license that meets your needs. |
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</p> |
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|
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<p> |
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If that isn't possible, if you really need a new license, with our |
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help you can ensure that the license really is a free software license |
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and avoid various practical problems. |
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</p> |
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|
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<h3 id="beyond-software">Beyond Software</h3> |
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|
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<p> |
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<a href="/philosophy/free-doc.html">Software manuals must be free</a>, |
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for the same reasons that software must be free, and because the |
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manuals are in effect part of the software. |
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</p> |
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|
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<p> |
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The same arguments also make sense for other kinds of works of |
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practical use — that is to say, works that embody useful knowledge, |
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such as educational works and reference |
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works. <a href="http://wikipedia.org">Wikipedia</a> is the best-known |
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example. |
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</p> |
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|
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<p> |
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Any kind of work <em>can</em> be free, and the definition of free software |
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has been extended to a definition of <a href="http://freedomdefined.org/"> |
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free cultural works</a> applicable to any kind of works. |
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</p> |
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|
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<h3 id="open-source">Open Source?</h3> |
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|
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<p> |
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Another group has started using the term “open source” to mean |
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something close (but not identical) to “free software”. We |
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prefer the term “free software” because, once you have heard that |
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it refers to freedom rather than price, it calls to mind freedom. The |
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word “open” <a href="/philosophy/open-source-misses-the-point.html"> |
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never refers to freedom</a>. |
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</p> |
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|
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<h3 id="History">History</h3> |
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|
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<p>From time to time we revise this Free Software Definition. Here is |
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the list of changes, along with links to show exactly what was |
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changed.</p> |
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|
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<ul> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.110&r2=1.111">Version |
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1.111</a>: Clarify 1.77 by saying that only |
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retroactive <em>restrictions</em> are unacceptable. The copyright |
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holders can always grant additional <em>permission</em> for use of the |
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work by releasing the work in another way in parallel.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.104&r2=1.105">Version |
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1.105</a>: Reflect, in the brief statement of freedom 1, the point |
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(already stated in version 1.80) that it includes really using your modified |
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version for your computing.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.91&r2=1.92">Version |
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1.92</a>: Clarify that obfuscated code does not qualify as source code.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.89&r2=1.90">Version |
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1.90</a>: Clarify that freedom 3 means the right to distribute copies |
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of your own modified or improved version, not a right to participate |
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in someone else's development project.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.88&r2=1.89">Version |
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1.89</a>: Freedom 3 includes the right to release modified versions as |
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free software.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.79&r2=1.80">Version |
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1.80</a>: Freedom 1 must be practical, not just theoretical; |
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i.e., no tivoization.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.76&r2=1.77">Version |
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1.77</a>: Clarify that all retroactive changes to the license are |
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unacceptable, even if it's not described as a complete |
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replacement.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.73&r2=1.74">Version |
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1.74</a>: Four clarifications of points not explicit enough, or stated |
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in some places but not reflected everywhere: |
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<ul> |
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<li>"Improvements" does not mean the license can |
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substantively limit what kinds of modified versions you can release. |
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Freedom 3 includes distributing modified versions, not just changes.</li> |
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<li>The right to merge in existing modules |
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refers to those that are suitably licensed.</li> |
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<li>Explicitly state the conclusion of the point about export controls.</li> |
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<li>Imposing a license change constitutes revoking the old license.</li> |
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</ul> |
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</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.56&r2=1.57">Version |
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1.57</a>: Add "Beyond Software" section.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.45&r2=1.46">Version |
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1.46</a>: Clarify whose purpose is significant in the freedom to run |
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the program for any purpose.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.40&r2=1.41">Version |
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1.41</a>: Clarify wording about contract-based licenses.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.39&r2=1.40">Version |
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1.40</a>: Explain that a free license must allow to you use other |
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available free software to create your modifications.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.38&r2=1.39">Version |
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1.39</a>: Note that it is acceptable for a license to require you to |
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provide source for versions of the software you put into public |
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use.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.30&r2=1.31">Version |
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1.31</a>: Note that it is acceptable for a license to require you to |
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identify yourself as the author of modifications. Other minor |
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clarifications throughout the text.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.22&r2=1.23">Version |
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1.23</a>: Address potential problems related to contract-based |
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licenses.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.15&r2=1.16">Version |
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1.16</a>: Explain why distribution of binaries is important.</li> |
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|
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.10&r2=1.11">Version |
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1.11</a>: Note that a free license may require you to send a copy of |
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versions you distribute to the author.</li> |
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|
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</ul> |
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|
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<p>There are gaps in the version numbers shown above because there are |
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other changes in this page that do not affect the definition as such. |
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These changes are in other parts of the page. You can review the |
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complete list of changes to the page through |
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the <a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&view=log">cvsweb |
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interface</a>.</p> |
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|
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</div> |
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|
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<!--#include virtual="/server/footer.html" --> |
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|
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<div id="footer"> |
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|
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<p> |
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Please send FSF & GNU inquiries to |
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<a href="mailto:gnu@gnu.org"><gnu@gnu.org></a>. |
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There are also <a href="/contact/">other ways to contact</a> |
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the FSF. |
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<br /> |
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Please send broken links and other corrections or suggestions to |
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<a href="mailto:webmasters@gnu.org"><webmasters@gnu.org></a>. |
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</p> |
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|
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<p> |
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Please see the |
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<a href="/server/standards/README.translations.html">Translations |
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README</a> for information on coordinating and submitting |
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translations of this article. |
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</p> |
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|
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<p> |
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Copyright © 1996-2002, 2004-2007, 2009, 2010, 2012 Free Software |
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Foundation, Inc. |
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</p> |
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<p>This page is licensed under a <a rel="license" |
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href="http://creativecommons.org/licenses/by-nd/3.0/us/">Creative |
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Commons Attribution-NoDerivs 3.0 United States License</a>. |
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</p> |
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|
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<!--#include virtual="/server/bottom-notes.html" --> |
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|
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<p>Updated: |
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<!-- timestamp start --> |
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$Date: 2012/07/01 10:12:02 $ |
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<!-- timestamp end --> |
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</p> |
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</div> |
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|
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|
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</div> |
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|
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</body> |
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</html> |