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A trivial export control requirement is not an actual problem.

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3 <title>What is free software? - GNU Project - Free Software Foundation (FSF)</title>
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12
13 <h2>What is free software?</h2>
14
15 <h3>The Free Software Definition</h3>
16
17 <blockquote>
18 <p>
19 The free software definition presents the criteria for whether a
20 particular software program qualifies as free software. From time to
21 time we revise this definition, to clarify it or to resolve questions
22 about subtle issues. See the <a href="#History">History section</a>
23 below for a list of changes that affect the definition of free
24 software.
25 </p>
26 </blockquote>
27
28 <p>
29 &ldquo;Free software&rdquo; means software that respects users'
30 freedom and community. Roughly, <b>the users have the freedom to run,
31 copy, distribute, study, change and improve the software</b>. With these
32 freedoms, the users (both individually and collectively) control the
33 program and what it does for them.
34 </p>
35
36 <p>
37 When users don't control the program, the program controls the users.
38 The developer controls the program, and through it controls the users.
39 This nonfree or &ldquo;proprietary&rdquo; program is therefore an
40 instrument of unjust power.
41 </p>
42
43 <p>
44 Thus, &ldquo;free software&rdquo; is a matter of liberty, not price.
45 To understand the concept, you should think of &ldquo;free&rdquo; as
46 in &ldquo;free speech,&rdquo; not as in &ldquo;free beer&rdquo;.
47 </p>
48
49 <p>
50 A program is free software if the program's users have the
51 four essential freedoms:
52 </p>
53
54 <ul>
55 <li>The freedom to run the program, for any purpose (freedom 0).</li>
56 <li>The freedom to study how the program works, and change it so it
57 does your computing as you wish (freedom 1). Access to the source
58 code is a precondition for this.
59 </li>
60 <li>The freedom to redistribute copies so you can help your neighbor
61 (freedom 2).
62 </li>
63 <li>The freedom to distribute copies of your modified versions
64 to others (freedom 3). By doing this you can give the whole
65 community a chance to benefit from your changes.
66 Access to the source code is a precondition for this.
67 </li>
68 </ul>
69
70 <p>
71 A program is free software if users have all of these freedoms. Thus,
72 you should be free to redistribute copies, either with or without
73 modifications, either gratis or charging a fee for distribution, to
74 <a href="#exportcontrol">anyone anywhere</a>. Being free to do these
75 things means (among other things) that you do not have to ask or pay
76 for permission to do so.
77 </p>
78
79 <p>
80 You should also have the freedom to make modifications and use them
81 privately in your own work or play, without even mentioning that they
82 exist. If you do publish your changes, you should not be required to
83 notify anyone in particular, or in any particular way.
84 </p>
85
86 <p>
87 The freedom to run the program means the freedom for any kind of person
88 or organization to use it on any kind of computer system, for any kind of
89 overall job and purpose, without being required to communicate about it
90 with the developer or any other specific entity. In this freedom, it is
91 the <em>user's</em> purpose that matters, not the <em>developer's</em>
92 purpose; you as a user are free to run the program for your purposes,
93 and if you distribute it to someone else, she is then free to run it
94 for her purposes, but you are not entitled to impose your purposes on her.
95 </p>
96
97 <p>
98 The freedom to redistribute copies must include binary or executable
99 forms of the program, as well as source code, for both modified and
100 unmodified versions. (Distributing programs in runnable form is necessary
101 for conveniently installable free operating systems.) It is OK if there
102 is no way to produce a binary or executable form for a certain program
103 (since some languages don't support that feature), but you must have the
104 freedom to redistribute such forms should you find or develop a way to
105 make them.
106 </p>
107
108 <p>
109 In order for freedoms 1 and 3 (the freedom to make changes and the
110 freedom to publish the changed versions) to be meaningful, you must have
111 access to the source code of the program. Therefore, accessibility of
112 source code is a necessary condition for free software. Obfuscated
113 &ldquo;source code&rdquo; is not real source code and does not count
114 as source code.
115 </p>
116
117 <p>
118 Freedom 1 includes the freedom to use your changed version in place of
119 the original. If the program is delivered in a product designed to
120 run someone else's modified versions but refuse to run yours &mdash; a
121 practice known as &ldquo;tivoization&rdquo; or &ldquo;lockdown&rdquo;,
122 or (in its practitioners' perverse terminology) as &ldquo;secure
123 boot&rdquo; &mdash; freedom 1 becomes a theoretical fiction rather
124 than a practical freedom. This is not sufficient. In other words,
125 these binaries are not free software even if the source code they are
126 compiled from is free.
127 </p>
128
129 <p>
130 One important way to modify a program is by merging in available free
131 subroutines and modules. If the program's license says that you
132 cannot merge in a suitably licensed existing module &mdash; for instance, if it
133 requires you to be the copyright holder of any code you add &mdash; then the
134 license is too restrictive to qualify as free.
135 </p>
136
137 <p>
138 Freedom 3 includes the freedom to release your modified versions
139 as free software. A free license may also permit other ways of
140 releasing them; in other words, it does not have to be
141 a <a href="/copyleft/copyleft.html">copyleft</a> license. However, a
142 license that requires modified versions to be nonfree does not qualify
143 as a free license.
144 </p>
145
146 <p>
147 In order for these freedoms to be real, they must be permanent and
148 irrevocable as long as you do nothing wrong; if the developer of the
149 software has the power to revoke the license, or retroactively add
150 restrictions to its terms, without your doing anything wrong to give
151 cause, the software is not free.
152 </p>
153
154 <p>
155 However, certain kinds of rules about the manner of distributing free
156 software are acceptable, when they don't conflict with the central
157 freedoms. For example, copyleft (very simply stated) is the rule that
158 when redistributing the program, you cannot add restrictions to deny
159 other people the central freedoms. This rule does not conflict with
160 the central freedoms; rather it protects them.
161 </p>
162
163 <p>
164 &ldquo;Free software&rdquo; does not mean &ldquo;noncommercial&rdquo;. A free
165 program must be available for commercial use, commercial development,
166 and commercial distribution. Commercial development of free software
167 is no longer unusual; such free commercial software is very important.
168 You may have paid money to get copies of free software, or you may have
169 obtained copies at no charge. But regardless of how you got your copies,
170 you always have the freedom to copy and change the software, even to
171 <a href="/philosophy/selling.html">sell copies</a>.
172 </p>
173
174 <p>
175 Whether a change constitutes an improvement is a subjective matter.
176 If your right to modify a program is limited, in substance, to changes that
177 someone else considers an improvement, that program is not free.
178 </p>
179
180 <p>
181 However, rules about how to package a modified version are acceptable,
182 if they don't substantively limit your freedom to release modified
183 versions, or your freedom to make and use modified versions privately.
184 Thus, it is acceptable for the license to require that you change the
185 name of the modified version, remove a logo, or identify your
186 modifications as yours. As long as these requirements are not so
187 burdensome that they effectively hamper you from releasing your
188 changes, they are acceptable; you're already making other changes to
189 the program, so you won't have trouble making a few more.
190 </p>
191
192 <p>
193 Rules that &ldquo;if you make your version available in this way, you
194 must make it available in that way also&rdquo; can be acceptable too,
195 on the same condition. An example of such an acceptable rule is one
196 saying that if you have distributed a
197 modified version and a previous developer asks for a copy of it, you
198 must send one. (Note that such a rule still leaves you the choice of
199 whether to distribute your version at all.) Rules that require release
200 of source code to the users for versions that you put into public use
201 are also acceptable.
202 </p>
203
204 <p>
205 A special issue arises when a license requires changing the name by
206 which the program will be invoked from other programs. That
207 effectively hampers you from releasing your changed version so that it
208 can replace the original when invoked by those other programs. This
209 sort of requirement is acceptable only if there's a suitable aliasing
210 facility that allows you to specify the original program's name as an
211 alias for the modified version.</p>
212
213 <p>
214 In the GNU project, we use
215 <a href="/copyleft/copyleft.html">copyleft</a>
216 to protect these freedoms legally for everyone. But
217 <a href="/philosophy/categories.html#Non-CopyleftedFreeSoftware">noncopylefted
218 free software</a> also exists. We believe there are important reasons why
219 <a href="/philosophy/pragmatic.html">it is better to use copyleft</a>,
220 but if your program is noncopylefted free software, it is still basically
221 ethical. (See <a href="/philosophy/categories.html">Categories of Free Software</a> for a description of how &ldquo;free software,&rdquo; &ldquo;copylefted software&rdquo; and other categories of software relate to each other.)
222 </p>
223
224 <p>
225 Sometimes government <a id="exportcontrol">export control regulations</a>
226 and trade sanctions can constrain your freedom to distribute copies of
227 programs internationally. Software developers do not have the power to
228 eliminate or override these restrictions, but what they can and must do
229 is refuse to impose them as conditions of use of the program. In this
230 way, the restrictions will not affect activities and people outside the
231 jurisdictions of these governments. Thus, free software licenses
232 must not require obedience to any nontrivial export regulations as a
233 condition of exercising any of the essential freedoms.
234 </p>
235
236 <p>
237 Merely mentioning the existence of export regulations, without making
238 them a condition of the license itself, is acceptable since it does
239 not restrict users. If an export regulation is actually trivial for
240 free software, then requiring it as a condition is not an actual
241 problem; however, it is a potential problem, since a later change in
242 export law could make the requirement nontrivial and thus render the
243 software nonfree.
244 </p>
245
246 <p>
247 Most free software licenses are based on copyright, and there are limits
248 on what kinds of requirements can be imposed through copyright. If a
249 copyright-based license respects freedom in the ways described above, it
250 is unlikely to have some other sort of problem that we never anticipated
251 (though this does happen occasionally). However, some free software
252 licenses are based on contracts, and contracts can impose a much larger
253 range of possible restrictions. That means there are many possible ways
254 such a license could be unacceptably restrictive and nonfree.
255 </p>
256
257 <p>
258 We can't possibly list all the ways that might happen. If a
259 contract-based license restricts the user in an unusual way that
260 copyright-based licenses cannot, and which isn't mentioned here as
261 legitimate, we will have to think about it, and we will probably conclude
262 it is nonfree.
263 </p>
264
265 <p>
266 When talking about free software, it is best to avoid using terms
267 like &ldquo;give away&rdquo; or &ldquo;for free,&rdquo; because those terms imply that
268 the issue is about price, not freedom. Some common terms such
269 as &ldquo;piracy&rdquo; embody opinions we hope you won't endorse. See
270 <a href="/philosophy/words-to-avoid.html">Confusing Words and Phrases that
271 are Worth Avoiding</a> for a discussion of these terms. We also have
272 a list of proper <a href="/philosophy/fs-translations.html">translations of
273 &ldquo;free software&rdquo;</a> into various languages.
274 </p>
275
276 <p>
277 Finally, note that criteria such as those stated in this free software
278 definition require careful thought for their interpretation. To decide
279 whether a specific software license qualifies as a free software license,
280 we judge it based on these criteria to determine whether it fits their
281 spirit as well as the precise words. If a license includes unconscionable
282 restrictions, we reject it, even if we did not anticipate the issue
283 in these criteria. Sometimes a license requirement raises an issue
284 that calls for extensive thought, including discussions with a lawyer,
285 before we can decide if the requirement is acceptable. When we reach
286 a conclusion about a new issue, we often update these criteria to make
287 it easier to see why certain licenses do or don't qualify.
288 </p>
289
290 <p>
291 If you are interested in whether a specific license qualifies as a free
292 software license, see our <a href="/licenses/license-list.html">list
293 of licenses</a>. If the license you are concerned with is not
294 listed there, you can ask us about it by sending us email at
295 <a href="mailto:licensing@gnu.org">&lt;licensing@gnu.org&gt;</a>.
296 </p>
297
298 <p>
299 If you are contemplating writing a new license, please contact the
300 Free Software Foundation first by writing to that address. The
301 proliferation of different free software licenses means increased work
302 for users in understanding the licenses; we may be able to help you
303 find an existing free software license that meets your needs.
304 </p>
305
306 <p>
307 If that isn't possible, if you really need a new license, with our
308 help you can ensure that the license really is a free software license
309 and avoid various practical problems.
310 </p>
311
312 <h3 id="beyond-software">Beyond Software</h3>
313
314 <p>
315 <a href="/philosophy/free-doc.html">Software manuals must be free</a>,
316 for the same reasons that software must be free, and because the
317 manuals are in effect part of the software.
318 </p>
319
320 <p>
321 The same arguments also make sense for other kinds of works of
322 practical use &mdash; that is to say, works that embody useful knowledge,
323 such as educational works and reference
324 works. <a href="http://wikipedia.org">Wikipedia</a> is the best-known
325 example.
326 </p>
327
328 <p>
329 Any kind of work <em>can</em> be free, and the definition of free software
330 has been extended to a definition of <a href="http://freedomdefined.org/">
331 free cultural works</a> applicable to any kind of works.
332 </p>
333
334 <h3 id="open-source">Open Source?</h3>
335
336 <p>
337 Another group has started using the term &ldquo;open source&rdquo; to mean
338 something close (but not identical) to &ldquo;free software&rdquo;. We
339 prefer the term &ldquo;free software&rdquo; because, once you have heard that
340 it refers to freedom rather than price, it calls to mind freedom. The
341 word &ldquo;open&rdquo; <a href="/philosophy/open-source-misses-the-point.html">
342 never refers to freedom</a>.
343 </p>
344
345 <h3 id="History">History</h3>
346
347 <p>From time to time we revise this Free Software Definition. Here is
348 the list of substantive changes, along with links to show exactly what
349 was changed.</p>
350
351 <ul>
352
353 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.121&amp;r2=1.122">Version
354 1.122</a>: An export control requirement is a real problem if the
355 requirement is nontrivial; otherwise it is only a potential problem.</li>
356
357 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.110&amp;r2=1.111">Version
358 1.111</a>: Clarify 1.77 by saying that only
359 retroactive <em>restrictions</em> are unacceptable. The copyright
360 holders can always grant additional <em>permission</em> for use of the
361 work by releasing the work in another way in parallel.</li>
362
363 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.104&amp;r2=1.105">Version
364 1.105</a>: Reflect, in the brief statement of freedom 1, the point
365 (already stated in version 1.80) that it includes really using your modified
366 version for your computing.</li>
367
368 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.91&amp;r2=1.92">Version
369 1.92</a>: Clarify that obfuscated code does not qualify as source code.</li>
370
371 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.89&amp;r2=1.90">Version
372 1.90</a>: Clarify that freedom 3 means the right to distribute copies
373 of your own modified or improved version, not a right to participate
374 in someone else's development project.</li>
375
376 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.88&amp;r2=1.89">Version
377 1.89</a>: Freedom 3 includes the right to release modified versions as
378 free software.</li>
379
380 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.79&amp;r2=1.80">Version
381 1.80</a>: Freedom 1 must be practical, not just theoretical;
382 i.e., no tivoization.</li>
383
384 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.76&amp;r2=1.77">Version
385 1.77</a>: Clarify that all retroactive changes to the license are
386 unacceptable, even if it's not described as a complete
387 replacement.</li>
388
389 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.73&amp;r2=1.74">Version
390 1.74</a>: Four clarifications of points not explicit enough, or stated
391 in some places but not reflected everywhere:
392 <ul>
393 <li>"Improvements" does not mean the license can
394 substantively limit what kinds of modified versions you can release.
395 Freedom 3 includes distributing modified versions, not just changes.</li>
396 <li>The right to merge in existing modules
397 refers to those that are suitably licensed.</li>
398 <li>Explicitly state the conclusion of the point about export controls.</li>
399 <li>Imposing a license change constitutes revoking the old license.</li>
400 </ul>
401 </li>
402
403 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.56&amp;r2=1.57">Version
404 1.57</a>: Add &quot;Beyond Software&quot; section.</li>
405
406 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.45&amp;r2=1.46">Version
407 1.46</a>: Clarify whose purpose is significant in the freedom to run
408 the program for any purpose.</li>
409
410 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.40&amp;r2=1.41">Version
411 1.41</a>: Clarify wording about contract-based licenses.</li>
412
413 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.39&amp;r2=1.40">Version
414 1.40</a>: Explain that a free license must allow to you use other
415 available free software to create your modifications.</li>
416
417 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.38&amp;r2=1.39">Version
418 1.39</a>: Note that it is acceptable for a license to require you to
419 provide source for versions of the software you put into public
420 use.</li>
421
422 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.30&amp;r2=1.31">Version
423 1.31</a>: Note that it is acceptable for a license to require you to
424 identify yourself as the author of modifications. Other minor
425 clarifications throughout the text.</li>
426
427 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.22&amp;r2=1.23">Version
428 1.23</a>: Address potential problems related to contract-based
429 licenses.</li>
430
431 <li><a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;r1=1.15&amp;r2=1.16">Version
432 1.16</a>: Explain why distribution of binaries is important.</li>
433
434 <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
435 1.11</a>: Note that a free license may require you to send a copy of
436 versions you distribute to the author.</li>
437
438 </ul>
439
440 <p>There are gaps in the version numbers shown above because there are
441 other changes in this page that do not affect the definition as such.
442 These changes are in other parts of the page. You can review the
443 complete list of changes to the page through
444 the <a href="http://web.cvs.savannah.gnu.org/viewvc/www/philosophy/free-sw.html?root=www&amp;view=log">cvsweb
445 interface</a>.</p>
446
447 </div>
448
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452
453 <p>
454 Please send FSF &amp; GNU inquiries to
455 <a href="mailto:gnu@gnu.org">&lt;gnu@gnu.org&gt;</a>.
456 There are also <a href="/contact/">other ways to contact</a>
457 the FSF.
458 <br />
459 Please send broken links and other corrections or suggestions to
460 <a href="mailto:webmasters@gnu.org">&lt;webmasters@gnu.org&gt;</a>.
461 </p>
462
463 <p>
464 Please see the
465 <a href="/server/standards/README.translations.html">Translations
466 README</a> for information on coordinating and submitting
467 translations of this article.
468 </p>
469
470 <p>
471 Copyright &copy; 1996-2002, 2004-2007, 2009, 2010, 2012 Free Software
472 Foundation, Inc.
473 </p>
474 <p>This page is licensed under a <a rel="license"
475 href="http://creativecommons.org/licenses/by-nd/3.0/us/">Creative
476 Commons Attribution-NoDerivs 3.0 United States License</a>.
477 </p>
478
479 <!--#include virtual="/server/bottom-notes.html" -->
480
481 <p>Updated:
482 <!-- timestamp start -->
483 $Date: 2013/05/27 03:49:32 $
484 <!-- timestamp end -->
485 </p>
486 </div>
487
488
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492 </html>

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