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-revision 1.146 by th_g,
Fri Jan  1 10:01:21 2016 UTC
+revision 1.169 by rms,
Tue Feb  2 23:19:19 2021 UTC
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- <!-- Parent-Version: 1.77 -->
+ <!-- Parent-Version: 1.86 -->
  <title>What is free software?
  - GNU Project - Free Software Foundation</title>
+ <style type="text/css" media="print,screen"><!--
+ .note { margin-left: 6%; margin-right: 6%; }
+ @media (min-width: 48em) {
+    .note { margin-top: .8em; }
+ }
+ --></style>
  <meta http-equiv="Keywords" content="GNU, FSF, Free Software Foundation, Linux, Emacs, GCC, Unix, Free Software, Operating System, GNU Kernel, HURD, GNU HURD, Hurd" />
  <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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  <!--#include virtual="/server/banner.html" -->
  <h2>What is free software?</h2>
- <!--#include virtual="/licenses/fsf-licensing.html" -->
+ <div class="article">
  <h3>The Free Software Definition</h3>
- <blockquote>
+ <blockquote class="note" id="fsf-licensing"><p style="font-size: 80%">
+ Have a question about free software licensing not answered here?
+ See our other <a href="http://www.fsf.org/licensing">licensing resources</a>,
+ and if necessary contact the FSF Compliance Lab
+ at <a href="mailto:licensing@fsf.org">licensing@fsf.org</a>.</p>
+ </blockquote>
+ <div class="comment">
  <p>
  The free software definition presents the criteria for whether a
  particular software program qualifies as free software.  From time to
-Line 23 
 about subtle issues.  See the <a href="#
+Line 35 
 about subtle issues.  See the <a href="#
  below for a list of changes that affect the definition of free
  software.
  </p>
- </blockquote>
+ <p>
+ &ldquo;Open source&rdquo; is something different: it has a very
+ different philosophy based on different values.  Its practical
+ definition is different too, but nearly all open source programs are
+ in fact free.  We explain the
+ difference in <a href="/philosophy/open-source-misses-the-point.html">
+ Why &ldquo;Open Source&rdquo; misses the point of Free Software</a>.
+ </p>
+ </div>
  <p>
  &ldquo;Free software&rdquo; means software that respects users'
-Line 33 
 software</b>.  Thus, &ldquo;free softwar
+Line 54 
 software</b>.  Thus, &ldquo;free softwar
  liberty, not price.  To understand the concept, you should think of
  &ldquo;free&rdquo; as in &ldquo;free speech,&rdquo; not as in
  &ldquo;free beer&rdquo;.  We sometimes call it &ldquo;libre
- software&rdquo; to show we do not mean it is gratis.
+ software,&rdquo; borrowing the French or Spanish word for
+ &ldquo;free&rdquo; as in freedom, to show we do not mean the software
+ is gratis.
  </p>
  <p>
-Line 47 
 program <a href="/philosophy/free-softwa
+Line 70 
 program <a href="/philosophy/free-softwa
  an instrument of unjust power</a>.
  </p>
+ <h4> The four essential freedoms</h4>
  <p>
  A program is free software if the program's users have the
- four essential freedoms:
+ four essential freedoms: <a href="#f1">[1]</a>
  </p>
- <ul>
+ <ul class="important">
    <li>The freedom to run the program as you wish,
        for any purpose (freedom 0).</li>
    <li>The freedom to study how the program works, and change it so it
        does your computing as you wish (freedom 1). Access to the source
        code is a precondition for this.
    </li>
-   <li>The freedom to redistribute copies so you can help your neighbor
+   <li>The freedom to redistribute copies so you can help others
        (freedom 2).
    </li>
    <li>The freedom to distribute copies of your modified versions
-Line 81 
 consider a program A which automatically
+Line 106 
 consider a program A which automatically
  handle some cases.  If we plan to distribute A as it stands, that
  implies users will need B, so we need to judge whether both A and B
  are free.  However, if we plan to modify A so that it doesn't use B,
- 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>
- <p>The rest of this page clarifies certain points about what makes
+ <p>
- specific freedoms adequate or not.</p>
+ &ldquo;Free software&rdquo; does not mean &ldquo;noncommercial&rdquo;.
+ On the contrary, a free program must be available for commercial use,
+ commercial development, and commercial distribution.  This policy is
+ of fundamental importance&mdash;without this, free software could not
+ achieve its aims.
+ </p>
- <p>Freedom to distribute (freedoms 2 and 3) means you are free to
+ <p>
- redistribute copies, either with or without modifications, either
+ We want to invite everyone to use the GNU system, including businesses
- gratis or charging a fee for distribution, to
+ and their workers.  That requires allowing commercial use.  We hope
- <a href="#exportcontrol">anyone anywhere</a>.  Being free to do these
+ that free replacement programs will supplant comparable proprietary
- 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
- for permission to do so.
+ them.  We want commercial products that contain software to include
+ the GNU system, and that would constitute commercial distribution for
+ a price.  Commercial development of free software is no longer
+ unusual; such free commercial software is very important.  Paid,
+ professional support for free software fills an important need.
  </p>
  <p>
- You should also have the freedom to make modifications and use them
+ Thus, to exclude commercial use, commercial development or commercial
- privately in your own work or play, without even mentioning that they
+ distribution would hobble the free software community and obstruct its
- 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
- notify anyone in particular, or in any particular way.
+ restrictions does not qualify as free software.
+ </p>
+ <p>
+ A free program must offer the four freedoms to any would-be user that
+ obtains a copy of the software, who has complied thus far with the
+ conditions of the free license covering the software in any previous
+ distribution of it.  Putting some of the freedoms off limits to some
+ users, or requiring that users pay, in money or in kind, to exercise
+ them, is tantamount to not granting the freedoms in question, and thus
+ renders the program nonfree.
  </p>
  <p>
+ You may have paid money to get copies of a free program, 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 <a href="/philosophy/selling.html">sell copies</a>.
+ </p>
+ <h3>Clarifying the line at various points</h3>
+ <p>In the rest of this article we explain more precisely how far the
+ various freedoms need to extend, on various issues, in order for a
+ program to be free.</p>
+ <h4>The freedom to run the program as you wish</h4>
+ <p>
  The freedom to run the 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 purpose, without being required to communicate about it
-Line 114 
 for her purposes, but you are not entitl
+Line 173 
 for her purposes, but you are not entitl
  <p>
  The freedom to run the program as you wish means that you are not
- 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
- functionality the program has, or whether it is useful for what you
+ functionality the program has, whether it is technically capable of
- want to do.</p>
+ functioning in any given environment, or whether it is useful for any
+ particular computing activity.</p>
+ <p>For example, if the code arbitrarily rejects certain meaningful
+ inputs&mdash;or even fails unconditionally&mdash;that may make the
+ program less useful, perhaps even totally useless, but it does not
+ deny users the freedom to run the program, so it does not conflict
+ with freedom 0.  If the program is free, the users can overcome the
+ loss of usefulness, because freedoms 1 and 3 permit users and
+ communities to make and distribute modified versions without the
+ arbitrary nuisance code.</p>
+ <p>&ldquo;As you wish&rdquo; includes, optonally, &ldquo;not at
+ all&rdquo; if that is what you wish.  So there is no need for a
+ separate &ldquo;freedom not to run a program.&rdquo;<p>
- <p>
+ <h4>The freedom to study the source code and make changes</h4>
- 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.
- </p>
  <p>
  In order for freedoms 1 and 3 (the freedom to make changes and the
- 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
  access to the source code of the program.  Therefore, accessibility of
  source code is a necessary condition for free software.  Obfuscated
  &ldquo;source code&rdquo; is not real source code and does not count
-Line 158 
 license is too restrictive to qualify as
+Line 222 
 license is too restrictive to qualify as
  </p>
  <p>
+ Whether a change constitutes an improvement is a subjective matter.
+ If your right to modify a program is limited, in substance, to changes that
+ someone else considers an improvement, that program is not free.
+ </p>
+ <p>
+ One special case of freedom 1 is to delete the program's code so it
+ returns after doing nothing, or make it invoke some other program.
+ Thus, freedom 1 includes the &ldquo;freedom to delete the program.&rdquo;
+ </p>
+ <h4>The freedom to redistribute if you wish: basic requirements</h4>
+ <p>Freedom to distribute (freedoms 2 and 3) means you are free to
+ redistribute copies, either with or without modifications, either
+ gratis or charging a fee for distribution, to
+ <a href="#exportcontrol">anyone anywhere</a>.  Being free to do these
+ things means (among other things) that you do not have to ask or pay
+ for permission to do so.
+ </p>
+ <p>
+ 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.
+ </p>
+ <p>
  Freedom 3 includes the freedom to 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
-Line 167 
 as a free license.
+Line 260 
 as a free license.
  </p>
  <p>
- In order for these freedoms to be real, they must be permanent and
+ The freedom to redistribute copies must include binary or executable
- 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
- software has the power to revoke the license, or retroactively add
+ unmodified versions.  (Distributing programs in runnable form is necessary
- restrictions to its terms, without your doing anything wrong to give
+ for conveniently installable free operating systems.)  It is OK if there
- cause, the software is not free.
+ 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.
  </p>
+ <h4>Copyleft</h4>
  <p>
- However, certain kinds of rules about the manner of distributing free
+ Certain kinds of rules about the manner of distributing free
  software are acceptable, when they don't conflict with the central
  freedoms.  For example, <a href="/copyleft/copyleft.html">copyleft</a>
  (very simply stated) is the rule that when redistributing the program,
-Line 197 
 Software</a> for a description of how &l
+Line 295 
 Software</a> for a description of how &l
  relate to each other.
  </p>
- <p>
+ <h4>Rules about packaging and distribution details</h4>
- &ldquo;Free software&rdquo; does not mean &ldquo;noncommercial&rdquo;.  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.
- 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
- <a href="/philosophy/selling.html">sell copies</a>.
- </p>
  <p>
- Whether a change constitutes an improvement is a subjective matter.
+ Rules about how to package a modified version are acceptable,
- If your right to modify a program is limited, in substance, to changes that
- someone else considers an improvement, that program is not free.
- </p>
- <p>
- 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.
  Thus, it is acceptable for the license to require that you change the
-Line 247 
 sort of requirement is acceptable only i
+Line 330 
 sort of requirement is acceptable only i
  facility that allows you to specify the original program's name as an
  alias for the modified version.</p>
+ <h4>Export regulations</h4>
  <p>
  Sometimes government <a id="exportcontrol">export control regulations</a>
  and trade sanctions can constrain your freedom to distribute copies of
-Line 269 
 export law could make the requirement no
+Line 354 
 export law could make the requirement no
  software nonfree.
  </p>
+ <h4>Legal considerations</h4>
+ <p>
+ 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 add
+ restrictions to its terms, without your doing anything wrong to give
+ cause, the software is not free.
+ </p>
  <p>
  A free license may not require compliance with the license of a
  nonfree program.  Thus, for instance, if a license requires you to
-Line 283 
 It is acceptable for a free license to s
+Line 378 
 It is acceptable for a free license to s
  law applies, or where litigation must be done, or both.
  </p>
+ <h4>Contract-based licenses</h4>
  <p>
  Most free software licenses are based on copyright, and there are limits
  on what kinds of requirements can be imposed through copyright.  If a
-Line 302 
 legitimate, we will have to think about
+Line 399 
 legitimate, we will have to think about
  it is nonfree.
  </p>
+ <h4>Use the right words when talking about free software</h4>
  <p>
  When talking about free software, it is best to avoid using terms
  like &ldquo;give away&rdquo; or &ldquo;for free,&rdquo; because those terms imply that
-Line 313 
 a list of proper <a href="/philosophy/fs
+Line 412 
 a list of proper <a href="/philosophy/fs
  &ldquo;free software&rdquo;</a> into various languages.
  </p>
+ <h4>How we interpret these criteria</h4>
  <p>
  Finally, note that criteria such as those stated in this free software
  definition require careful thought for their interpretation.  To decide
-Line 327 
 a conclusion about a new issue, we often
+Line 428 
 a conclusion about a new issue, we often
  it easier to see why certain licenses do or don't qualify.
  </p>
+ <h4>Get help with free licenses</h4>
  <p>
  If you are interested in whether a specific license qualifies as a free
  software license, see our <a href="/licenses/license-list.html">list
-Line 381 
 it refers to freedom rather than price,
+Line 484 
 it refers to freedom rather than price,
  word &ldquo;open&rdquo; <a href="/philosophy/open-source-misses-the-point.html">
  never refers to freedom</a>.
  </p>
+ </div>
  <h3 id="History">History</h3>
-Line 390 
 was changed.</p>
+Line 494 
 was changed.</p>
  <ul>
+ <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.168&amp;r2=1.169">Version
+.169</a>: Explain why more clearly why the four freedoms must apply
+ to commercial activity.  Explain why the four freedoms imply the
+ freedom not to run the program and the freedom to delete it, so there
+ is no need to state those as separate requirements.</li>
+ <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.164&amp;r2=1.165">Version
+.165</a>: Clarify that arbitrary annoyances in the code do not
+ negate freedom 0, and that freedoms 1 and 3 enable users to remove them.</li>
+ <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.152&amp;r2=1.153">Version
+.153</a>: Clarify that freedom to run the program means nothing stops
+ you from making it run.</li>
  <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.140&amp;r2=1.141">Version
 .141</a>: Clarify which code needs to be free.</li>
-Line 496 
 licenses.</li>
+Line 614 
 licenses.</li>
  <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.10&amp;r2=1.11">Version
 .11</a>: Note that a free license may require you to send a copy of
- versions you distribute to the author.</li>
+ versions you distribute to previous developers on request.</li>
  </ul>
-Line 508 
 You can review the complete list of chan
+Line 626 
 You can review the complete list of chan
  the <a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;view=log">cvsweb
  interface</a>.</p>
+ <h3 style="font-size:1em">Footnote</h3>
+ <ol>
+ <li id="f1">The reason they are numbered 0, 1, 2 and 3 is historical. Around
+there were three freedoms, numbered 1, 2 and 3. Then we realized that
+ the freedom to run the program needed to be mentioned explicitly.
+ It was clearly more basic than the other three, so it properly should
+ precede them. Rather than renumber the others, we made it freedom&nbsp;0.</li>
+ </ol>
  </div><!-- for id="content", starts in the include above -->
  <!--#include virtual="/server/footer.html" -->
-Line 556 
 of this article.</p>
+Line 682 
 of this article.</p>
       There is more detail about copyright years in the GNU Maintainers
       Information document, www.gnu.org/prep/maintain. -->
- <p>Copyright &copy; 1996, 2002, 2004-2007, 2009-2015
+ <p>Copyright &copy; 1996, 2002, 2004-2007, 2009-2019
  Free Software Foundation, Inc.</p>
  <p>This page is licensed under a <a rel="license"
-Line 571 
 $Date$
+Line 697 
 $Date$
  <!-- timestamp end -->
  </p>
  </div>
- </div>
+ </div><!-- for class="inner", starts in the banner include -->
  </body>
  </html>

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