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<title>What is free software? |
<title>What is free software? |
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- GNU Project - Free Software Foundation</title> |
- GNU Project - Free Software Foundation</title> |
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<meta http-equiv="Description" content="Since 1983, developing the free Unix style operating system GNU, so that computer users can have the freedom to share and improve the software they use." /> |
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<h2>What is free software?</h2> |
<h2>What is free software?</h2> |
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<div class="article"> |
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<h3>The Free Software Definition</h3> |
<h3>The Free Software Definition</h3> |
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<blockquote> |
<blockquote class="note" id="fsf-licensing"><p style="font-size: 80%"> |
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Have a question about free software licensing not answered here? |
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See our other <a href="http://www.fsf.org/licensing">licensing resources</a>, |
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and if necessary contact the FSF Compliance Lab |
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at <a href="mailto:licensing@fsf.org">licensing@fsf.org</a>.</p> |
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</blockquote> |
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<div class="comment"> |
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<p> |
<p> |
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The free software definition presents the criteria for whether a |
The free software definition presents the criteria for whether a |
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particular software program qualifies as free software. From time to |
particular software program qualifies as free software. From time to |
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below for a list of changes that affect the definition of free |
below for a list of changes that affect the definition of free |
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software. |
software. |
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</p> |
</p> |
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</blockquote> |
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<p> |
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“Open source” is something different: it has a very |
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different philosophy based on different values. Its practical |
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definition is different too, but nearly all open source programs are |
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in fact free. We explain the |
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difference in <a href="/philosophy/open-source-misses-the-point.html"> |
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Why “Open Source” misses the point of Free Software</a>. |
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</p> |
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</div> |
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<p> |
<p> |
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“Free software” means software that respects users' |
“Free software” means software that respects users' |
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liberty, not price. To understand the concept, you should think of |
liberty, not price. To understand the concept, you should think of |
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“free” as in “free speech,” not as in |
“free” as in “free speech,” not as in |
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“free beer”. We sometimes call it “libre |
“free beer”. We sometimes call it “libre |
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software” to show we do not mean it is gratis. |
software,” borrowing the French or Spanish word for |
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“free” as in freedom, to show we do not mean the software |
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is gratis. |
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</p> |
</p> |
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<p> |
<p> |
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an instrument of unjust power</a>. |
an instrument of unjust power</a>. |
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</p> |
</p> |
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<h4> The four essential freedoms</h4> |
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|
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<p> |
<p> |
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A program is free software if the program's users have the |
A program is free software if the program's users have the |
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four essential freedoms: |
four essential freedoms: <a href="#f1">[1]</a> |
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</p> |
</p> |
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|
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<ul> |
<ul class="important"> |
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<li>The freedom to run the program as you wish, |
<li>The freedom to run the program as you wish, |
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for any purpose (freedom 0).</li> |
for any purpose (freedom 0).</li> |
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<li>The freedom to study how the program works, and change it so it |
<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 |
does your computing as you wish (freedom 1). Access to the source |
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code is a precondition for this. |
code is a precondition for this. |
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</li> |
</li> |
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<li>The freedom to redistribute copies so you can help your neighbor |
<li>The freedom to redistribute copies so you can help others |
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(freedom 2). |
(freedom 2). |
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</li> |
</li> |
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<li>The freedom to distribute copies of your modified versions |
<li>The freedom to distribute copies of your modified versions |
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handle some cases. If we plan to distribute A as it stands, that |
handle some cases. If we plan to distribute A as it stands, that |
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implies users will need B, so we need to judge whether both A and B |
implies users will need B, so we need to judge whether both A and B |
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are free. However, if we plan to modify A so that it doesn't use B, |
are free. However, if we plan to modify A so that it doesn't use B, |
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only A needs to be free; we can ignore B.</p> |
only A needs to be free; B is not pertinent to that plan.</p> |
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<p>The rest of this page clarifies certain points about what makes |
<p> |
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specific freedoms adequate or not.</p> |
“Free software” does not mean “noncommercial”. |
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On the contrary, a free program must be available for commercial use, |
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commercial development, and commercial distribution. This policy is |
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of fundamental importance—without this, free software could not |
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achieve its aims. |
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</p> |
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<p>Freedom to distribute (freedoms 2 and 3) means you are free to |
<p> |
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redistribute copies, either with or without modifications, either |
We want to invite everyone to use the GNU system, including businesses |
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gratis or charging a fee for distribution, to |
and their workers. That requires allowing commercial use. We hope |
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<a href="#exportcontrol">anyone anywhere</a>. Being free to do these |
that free replacement programs will supplant comparable proprietary |
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things means (among other things) that you do not have to ask or pay |
programs, but they can't do that if businesses are forbidden to use |
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for permission to do so. |
them. We want commercial products that contain software to include |
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the GNU system, and that would constitute commercial distribution for |
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a price. Commercial development of free software is no longer |
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unusual; such free commercial software is very important. Paid, |
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professional support for free software fills an important need. |
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</p> |
</p> |
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<p> |
<p> |
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You should also have the freedom to make modifications and use them |
Thus, to exclude commercial use, commercial development or commercial |
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privately in your own work or play, without even mentioning that they |
distribution would hobble the free software community and obstruct its |
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exist. If you do publish your changes, you should not be required to |
path to success. We must conclude that a program licensed with such |
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notify anyone in particular, or in any particular way. |
restrictions does not qualify as free software. |
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</p> |
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<p> |
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A free program must offer the four freedoms to any would-be user that |
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obtains a copy of the software, who has complied thus far with the |
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conditions of the free license covering the software in any previous |
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distribution of it. Putting some of the freedoms off limits to some |
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users, or requiring that users pay, in money or in kind, to exercise |
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them, is tantamount to not granting the freedoms in question, and thus |
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renders the program nonfree. |
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</p> |
</p> |
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<p> |
<p> |
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You may have paid money to get copies of a free program, or you may |
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have obtained copies at no charge. But regardless of how you got your |
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copies, you always have the freedom to copy and change the software, |
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even to <a href="/philosophy/selling.html">sell copies</a>. |
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</p> |
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<h3>Clarifying the line at various points</h3> |
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<p>In the rest of this article we explain more precisely how far the |
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various freedoms need to extend, on various issues, in order for a |
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program to be free.</p> |
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<h4>The freedom to run the program as you wish</h4> |
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<p> |
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The freedom to run the program means the freedom for any kind of person |
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 |
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 |
overall job and purpose, without being required to communicate about it |
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<p> |
<p> |
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The freedom to run the program as you wish means that you are not |
The freedom to run the program as you wish means that you are not |
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forbidden or stopped from doing so. It has nothing to do with what |
forbidden or stopped from making it run. This has nothing to do with what |
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functionality the program has, or whether it is useful for what you |
functionality the program has, whether it is technically capable of |
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want to do.</p> |
functioning in any given environment, or whether it is useful for any |
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particular computing activity.</p> |
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<p>For example, if the code arbitrarily rejects certain meaningful |
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inputs—or even fails unconditionally—that may make the |
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program less useful, perhaps even totally useless, but it does not |
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deny users the freedom to run the program, so it does not conflict |
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with freedom 0. If the program is free, the users can overcome the |
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loss of usefulness, because freedoms 1 and 3 permit users and |
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communities to make and distribute modified versions without the |
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arbitrary nuisance code.</p> |
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<p>“As you wish” includes, optonally, “not at |
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all” if that is what you wish. So there is no need for a |
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separate “freedom not to run a program.”<p> |
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<p> |
<h4>The freedom to study the source code and make changes</h4> |
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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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<p> |
<p> |
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In order for freedoms 1 and 3 (the freedom to make changes and the |
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 |
freedom to publish the changed versions) to be meaningful, you need to have |
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access to the source code of the program. Therefore, accessibility of |
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 |
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 |
“source code” is not real source code and does not count |
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</p> |
</p> |
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<p> |
<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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<p> |
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One special case of freedom 1 is to delete the program's code so it |
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returns after doing nothing, or make it invoke some other program. |
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Thus, freedom 1 includes the “freedom to delete the program.” |
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</p> |
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<h4>The freedom to redistribute if you wish: basic requirements</h4> |
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<p>Freedom to distribute (freedoms 2 and 3) means you are free to |
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redistribute copies, either with or without modifications, either |
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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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<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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<p> |
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Freedom 3 includes the freedom to release your modified versions |
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 |
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 |
releasing them; in other words, it does not have to be |
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</p> |
</p> |
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<p> |
<p> |
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In order for these freedoms to be real, they must be permanent and |
The freedom to redistribute copies must include binary or executable |
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irrevocable as long as you do nothing wrong; if the developer of the |
forms of the program, as well as source code, for both modified and |
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software has the power to revoke the license, or retroactively add |
unmodified versions. (Distributing programs in runnable form is necessary |
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restrictions to its terms, without your doing anything wrong to give |
for conveniently installable free operating systems.) It is OK if there |
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cause, the software is not free. |
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> |
</p> |
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<h4>Copyleft</h4> |
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<p> |
<p> |
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However, certain kinds of rules about the manner of distributing free |
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 |
software are acceptable, when they don't conflict with the central |
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freedoms. For example, <a href="/copyleft/copyleft.html">copyleft</a> |
freedoms. For example, <a href="/copyleft/copyleft.html">copyleft</a> |
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(very simply stated) is the rule that when redistributing the program, |
(very simply stated) is the rule that when redistributing the program, |
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relate to each other. |
relate to each other. |
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</p> |
</p> |
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<p> |
<h4>Rules about packaging and distribution details</h4> |
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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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<p> |
<p> |
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Whether a change constitutes an improvement is a subjective matter. |
Rules about how to package a modified version are acceptable, |
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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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<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 |
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. |
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 |
Thus, it is acceptable for the license to require that you change the |
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facility that allows you to specify the original program's name as an |
facility that allows you to specify the original program's name as an |
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alias for the modified version.</p> |
alias for the modified version.</p> |
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<h4>Export regulations</h4> |
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<p> |
<p> |
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Sometimes government <a id="exportcontrol">export control regulations</a> |
Sometimes government <a id="exportcontrol">export control regulations</a> |
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and trade sanctions can constrain your freedom to distribute copies of |
and trade sanctions can constrain your freedom to distribute copies of |
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software nonfree. |
software nonfree. |
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</p> |
</p> |
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<h4>Legal considerations</h4> |
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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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<p> |
<p> |
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A free license may not require compliance with the license of a |
A free license may not require compliance with the license of a |
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nonfree program. Thus, for instance, if a license requires you to |
nonfree program. Thus, for instance, if a license requires you to |
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law applies, or where litigation must be done, or both. |
law applies, or where litigation must be done, or both. |
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</p> |
</p> |
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<h4>Contract-based licenses</h4> |
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<p> |
<p> |
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Most free software licenses are based on copyright, and there are limits |
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 |
on what kinds of requirements can be imposed through copyright. If a |
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it is nonfree. |
it is nonfree. |
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</p> |
</p> |
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<h4>Use the right words when talking about free software</h4> |
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<p> |
<p> |
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When talking about free software, it is best to avoid using terms |
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 |
like “give away” or “for free,” because those terms imply that |
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“free software”</a> into various languages. |
“free software”</a> into various languages. |
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</p> |
</p> |
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<h4>How we interpret these criteria</h4> |
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<p> |
<p> |
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Finally, note that criteria such as those stated in this free software |
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 |
definition require careful thought for their interpretation. To decide |
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it easier to see why certain licenses do or don't qualify. |
it easier to see why certain licenses do or don't qualify. |
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</p> |
</p> |
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<h4>Get help with free licenses</h4> |
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<p> |
<p> |
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If you are interested in whether a specific license qualifies as a free |
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 |
software license, see our <a href="/licenses/license-list.html">list |
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word “open” <a href="/philosophy/open-source-misses-the-point.html"> |
word “open” <a href="/philosophy/open-source-misses-the-point.html"> |
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never refers to freedom</a>. |
never refers to freedom</a>. |
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</p> |
</p> |
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</div> |
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<h3 id="History">History</h3> |
<h3 id="History">History</h3> |
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<ul> |
<ul> |
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.168&r2=1.169">Version |
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1.169</a>: Explain why more clearly why the four freedoms must apply |
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to commercial activity. Explain why the four freedoms imply the |
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freedom not to run the program and the freedom to delete it, so there |
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is no need to state those as separate requirements.</li> |
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.164&r2=1.165">Version |
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1.165</a>: Clarify that arbitrary annoyances in the code do not |
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negate freedom 0, and that freedoms 1 and 3 enable users to remove them.</li> |
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<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.152&r2=1.153">Version |
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1.153</a>: Clarify that freedom to run the program means nothing stops |
509 |
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you from making it run.</li> |
510 |
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511 |
<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.140&r2=1.141">Version |
<li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&r1=1.140&r2=1.141">Version |
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1.141</a>: Clarify which code needs to be free.</li> |
1.141</a>: Clarify which code needs to be free.</li> |
513 |
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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 |
<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 |
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> |
versions you distribute to previous developers on request.</li> |
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</ul> |
</ul> |
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|
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the <a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&view=log">cvsweb |
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> |
interface</a>.</p> |
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<h3 style="font-size:1em">Footnote</h3> |
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<ol> |
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<li id="f1">The reason they are numbered 0, 1, 2 and 3 is historical. Around |
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1990 there were three freedoms, numbered 1, 2 and 3. Then we realized that |
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the freedom to run the program needed to be mentioned explicitly. |
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It was clearly more basic than the other three, so it properly should |
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precede them. Rather than renumber the others, we made it freedom 0.</li> |
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</ol> |
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</div><!-- for id="content", starts in the include above --> |
</div><!-- for id="content", starts in the include above --> |
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<!--#include virtual="/server/footer.html" --> |
<!--#include virtual="/server/footer.html" --> |
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There is more detail about copyright years in the GNU Maintainers |
There is more detail about copyright years in the GNU Maintainers |
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Information document, www.gnu.org/prep/maintain. --> |
Information document, www.gnu.org/prep/maintain. --> |
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|
|
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<p>Copyright © 1996, 2002, 2004-2007, 2009-2015 |
<p>Copyright © 1996, 2002, 2004-2007, 2009-2019 |
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Free Software Foundation, Inc.</p> |
Free Software Foundation, Inc.</p> |
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|
|
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<p>This page is licensed under a <a rel="license" |
<p>This page is licensed under a <a rel="license" |
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<!-- timestamp end --> |
<!-- timestamp end --> |
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</p> |
</p> |
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</div> |
</div> |
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</div> |
</div><!-- for class="inner", starts in the banner include --> |
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</body> |
</body> |
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</html> |
</html> |