The Free Software Definition

+We maintain this free software definition to show clearly what must be +true about a particular software program for it to be considered free +software. From time to time we revise this definition to clarify it. +If you would like to review the changes we've made, please see +the History section below for more information.

-We maintain this free software definition to show clearly what must be -true about a particular software program for it to be considered -free software.

-``Free software'' is a matter of liberty, not price. To understand the -concept, you should think of ``free'' as in ``free speech,'' not as in -``free beer.''

-Free software is a matter of the users' freedom to run, copy, -distribute, study, change and improve the software. More precisely, -it refers to four kinds of freedom, for the users of the software:

-A program is free software if users have all of these freedoms. -Thus, you should be free to redistribute copies, either with or -without modifications, either gratis or charging a fee for -distribution, to anyone anywhere. Being -free to do these things means (among other things) that you do not -have to ask or pay for permission.

You should also have the freedom to make modifications and use them privately in your own work or play, without even mentioning that they exist. If you do publish your changes, you should not be required to -notify anyone in particular, or in any particular way.

-The freedom to use a program means the freedom for any kind of person -or organization to use it on any kind of computer system, for any kind -of overall job, and without being required to communicate subsequently -with the developer or any other specific entity.

The freedom to redistribute copies must include binary or executable forms of the program, as well as source code, for both modified and -unmodified versions. (Distributing programs in runnable form is -necessary for conveniently installable free operating systems.) It is -ok if there is no way to produce a binary or executable form for a -certain program (since some languages don't support that feature), but -you must have the freedom to redistribute such forms should you find -or develop a way to make them.

-In order for the freedoms to make changes, and to publish improved -versions, to be meaningful, you must have access to the source code of -the program. Therefore, accessibility of source code is a necessary -condition for free software.

-In order for these freedoms to be real, they must be irrevocable as -long as you do nothing wrong; if the developer of the software has the -power to revoke the license, without your doing anything to give -cause, the software is not free.

+In order for freedoms 1 and 3 (the freedom to make changes and the +freedom to publish improved versions) to be meaningful, you must have +access to the source code of the program. Therefore, accessibility of +source code is a necessary condition for free software. +

+Freedom 1 includes the freedom to use your changed version in place of +the original. If the program is delivered in a product designed to +run someone else's modified versions but refuse to run yours — +a practice known as “tivoization” or (through +blacklisting) as “secure boot” — freedom 1 becomes a +theoretical fiction rather than a practical freedom. This is not +sufficient. In other words, these binaries are not free software +even if the source code they are compiled from is free. +

+One important way to modify a program is by merging in available free +subroutines and modules. If the program's license says that you +cannot merge in a suitably licensed existing module — for instance, if it +requires you to be the copyright holder of any code you add — then the +license is too restrictive to qualify as free. +

+Freedom 3 includes the freedom to use release your modified versions +as free software. A free license may also permit other ways of +releasing them; in other words, it does not have to be +a copyleft license. However, a +license that requires modified versions to be nonfree does not qualify +as a free license. +

+In order for these freedoms to be real, they must be permanent and +irrevocable as long as you do nothing wrong; if the developer of the +software has the power to revoke the license, or retroactively change +its terms, without your doing anything wrong to give cause, the +software is not free. +

However, certain kinds of rules about the manner of distributing free software are acceptable, when they don't conflict with the central freedoms. For example, copyleft (very simply stated) is the rule that when redistributing the program, you cannot add restrictions to deny other people the central freedoms. This rule does not conflict with -the central freedoms; rather it protects them.

-Thus, you may have paid money to get copies of free software, or you -may have obtained copies at no charge. But regardless of how you got -your copies, you always have the freedom to copy and change the -software, even to sell copies.

-``Free software'' does not mean ``non-commercial''. A free program -must be available for commercial use, commercial development, and -commercial distribution. Commercial development of free software is -no longer unusual; such free commercial software is very important.

-Rules about how to package a modified version are acceptable, if they -don't effectively block your freedom to release modified versions. -Rules that ``if you make the program available in this way, you must -make it available in that way also'' can be acceptable too, on the -same condition. (Note that such a rule still leaves you the choice of -whether to publish the program or not.) It is also acceptable for the -license to require that, if you have distributed a modified version -and a previous developer asks for a copy of it, you must send one.

+Whether a change constitutes an improvement is a subjective matter. +If your modifications are limited, in substance, to changes that +someone else considers an improvement, that is not freedom. +

+However, rules about how to package a modified version are acceptable, if they +don't substantively limit your freedom to release modified versions, or +your freedom to make and use modified versions privately. Rules that if +you make your version available in this way, you must make it available in +that way also can be acceptable too, on the same condition. (Note that +such a rule still leaves you the choice of whether to publish your version +at all.) Rules that require release of source code to the users for +versions that you put into public use are also acceptable. It is also +acceptable for the license to require that you identify +your modifications as yours, or that, if you have distributed a modified +version and a previous developer asks for a copy of it, you must send +one. +

-In the GNU project, we use ``copyleft'' -to protect these freedoms legally for everyone. But +In the GNU project, we use +copyleft +to protect these freedoms legally for everyone. But non-copylefted -free software also exists. We believe there are -important reasons why it is -better to use copyleft, but if your program is non-copylefted free -software, we can still use it.

See Categories of Free Software -for a description of how ``free software,'' ``copylefted software'' and -other categories of software relate to each other.

-Sometimes government export control -regulations and trade sanctions can constrain your freedom to -distribute copies of programs internationally. Software developers do -not have the power to eliminate or override these restrictions, but -what they can and must do is refuse to impose them as conditions of -use of the program. In this way, the restrictions will not affect -activities and people outside the jurisdictions of these governments.

-Most free software licenses are based on copyright, and there are -limits on what kinds of requirements can be imposed through copyright. -If a copyright-based license respects freedom in the ways described -above, it is unlikely to have some other sort of problem that we never -anticipated (though this does happen occasionally). However, some -free software licenses are based on contracts, and contracts can -impose a much larger range of possible restrictions. That means there -are many possible ways such a license could be unacceptably -restrictive and non-free.

-We can't possibly list all the possible contract restrictions that -would be unacceptable. If a contract-based license restricts the user -in an unusual way that copyright-based licenses cannot, and which -isn't mentioned here as legitimate, we will have to think about it, -and we will probably decide it is non-free.

-When talking about free software, it is best to avoid using terms like -``give away'' or ``for free'', because those terms imply that the -issue is about price, not freedom. Some common terms such as -``piracy'' embody opinions we hope you won't endorse. See -Confusing Words and Phrases -that are Worth Avoiding for a discussion of these terms. -We also have a list of translations -of "free software" into various languages.

+Most free software licenses are based on copyright, and there are limits +on what kinds of requirements can be imposed through copyright. If a +copyright-based license respects freedom in the ways described above, it +is unlikely to have some other sort of problem that we never anticipated +(though this does happen occasionally). However, some free software +licenses are based on contracts, and contracts can impose a much larger +range of possible restrictions. That means there are many possible ways +such a license could be unacceptably restrictive and nonfree. +

+We can't possibly list all the ways that might happen. If a +contract-based license restricts the user in an unusual way that +copyright-based licenses cannot, and which isn't mentioned here as +legitimate, we will have to think about it, and we will probably conclude +it is nonfree. +

+When talking about free software, it is best to avoid using terms +like give away or for free, because those terms imply that +the issue is about price, not freedom. Some common terms such +as piracy embody opinions we hope you won't endorse. See +Confusing Words and Phrases that +are Worth Avoiding for a discussion of these terms. We also have +a list of proper translations of +free software into various languages. +

Finally, note that criteria such as those stated in this free software -definition require careful thought for their interpretation. To -decide whether a specific software license qualifies as a free -software license, we judge it based on these criteria to determine -whether it fits their spirit as well as the precise words. If a -license includes unconscionable restrictions, we reject it, even if we -did not anticipate the issue in these criteria. Sometimes a license -requirement raises an issue that calls for extensive thought, -including discussions with a lawyer, before we can decide if the -requirement is acceptable. When we reach a conclusion about a new -issue, we often update these criteria to make it easier to see why -certain licenses do or don't qualify.

-If you are interested in whether a specific license qualifies as a -free software license, see our list -of licenses. If the -license you are concerned with is not listed there, you can ask us -about it by sending us email -at <licensing@gnu.org>.

-Another group has started using the term "open source" to mean -something close (but not identical) to "free software". We prefer the -term "free software" because, once you have heard it refers to freedom -rather than price, it calls -to mind freedom.

Beyond Software

+ +

+Software manuals must be free, +for the same reasons that software must be free, and because the +manuals are in effect part of the software. +

+ +

+The same arguments also make sense for other kinds of works of +practical use — that is to say, works that embody useful knowledge, +such as educational works and reference +works. Wikipedia is the best known +example.

-Return to the GNU Project home page. +Any kind of work can be free, and the definition of free software +has been extended to a definition of +free cultural works applicable to any kind of works.

Open Source?

+ +

+Another group has started using the term open source to mean +something close (but not identical) to free software. We +prefer the term free software because, once you have heard that +it refers to freedom rather than price, it calls to mind freedom. The +word open +never refers to freedom. +

+ +

History

+ +

From time to time we revise this Free Software Definition to +clarify it. Here we provide a list of those modifications, along with +links to illustrate exactly what changed, so that others can review +them if they like.

+ +

Version +1.90: Clarify that freedom 3 means the right to distribute copies +of your own modified or improved version, not a right to participate +in someone else's development project.
Version +1.89: Freedom 3 includes the right to release modified versions as +free software.
Version +1.80: Freedom 1 must be practical, not just theoretical; +i.e., no tivoization.
Version +1.77: Clarify that all retroactive changes to the license are +unacceptable, even if it's not described as a complete +replacement.
Version +1.74: Four clarifications of points not explicit enough, or stated +in some places but not reflected everywhere: +
- "Improvements" does not mean the license can +substantively limit what kinds of modified versions you can release. +Freedom 3 includes distributing modified versions, not just changes.
- The right to merge in existing modules +refers to those that are suitably licensed.
- Explicitly state the conclusion of the point about export controls.
- Imposing a license change constitutes revoking the old license.
+
Version +1.57: Add "Beyond Software" section.
Version +1.46: Clarify whose purpose is significant in the freedom to run +the program for any purpose.
Version +1.41: Clarify wording about contract-based licenses.
Version +1.40: Explain that a free license must allow to you use other +available free software to create your modifications.
Version +1.39: Note that it is acceptable for a license to require you to +provide source for versions of the software you put into public +use.
Version +1.31: Note that it is acceptable for a license to require you to +identify yourself as the author of modifications. Other minor +clarifications throughout the text.
Version +1.23: Address potential problems related to contract-based +licenses.
Version +1.16: Explain why distribution of binaries is important.
Version +1.11: Note that a free license may require you to send a copy of +versions you distribute to the author.

+ +

There are gaps in the version numbers because there are many other +changes that do not affect the substance of the definition at all. +Instead, they fix links, add translations, and so on. If you would +like to review the complete list of changes, you can do so on +our cvsweb +interface.

+ +

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