What is Free Software? +- GNU Project - Free Software Foundation

What is Free Software?

+ +

+“Free software” means software that respects users' +freedom and community. Roughly, it means that the users have the +freedom to run, copy, distribute, study, change and improve the +software. Thus, “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.” We sometimes call it “libre +software,” borrowing the French or Spanish word for +“free” as in freedom, to show we do not mean the software +is gratis. +

- -The Free Software Definition - GNU Project - Free Software Foundation (FSF) - - - - +

+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 sell copies. +

- - - - - +

+We campaign for these freedoms because everyone deserves them. With +these freedoms, the users (both individually and collectively) control +the program and what it does for them. When users don't control the +program, we call it a “nonfree” or +“proprietary” program. The nonfree program controls the +users, and the developer controls the program; this makes the +program +an instrument of unjust power. +

- +

+“Open source” 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 +Why “Open Source” misses the point of Free Software. +

Translations of this page

The Free Software Definition +
- The four essential freedoms
- Free software can be commercial
+
Clarifying the Boundary Between Free and Nonfree +
+
The Free Software Definition in Practice +
+
Beyond Software
History

+ + + + +

The Free Software Definition

- +The free software definition presents the criteria for whether a +particular software program qualifies as free software. From time to +time we revise this definition, to clarify it or to resolve questions +about subtle issues. See the History section +below for a list of changes that affect the definition of free +software.

The four essential freedoms

-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.

+A program is free software if the program's users have the +four essential freedoms: [1] +

+ +

The freedom to run the program as you wish, + for any purpose (freedom 0).
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. +
The freedom to redistribute copies so you can help others + (freedom 2). +
The freedom to distribute copies of your modified versions + to others (freedom 3). By doing this you can give the whole + community a chance to benefit from your changes. + Access to the source code is a precondition for this. +

-``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.''

+A program is free software if it gives users adequately all of these +freedoms. Otherwise, it is nonfree. While we can distinguish various +nonfree distribution schemes in terms of how far they fall short of +being free, we consider them all equally unethical.

+ +

In any given scenario, these freedoms must apply to whatever code +we plan to make use of, or lead others to make use of. For instance, +consider a program A which automatically launches a program B to +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; B is not pertinent to that plan.

+ + +

Free software can be commercial

+ +

+“Free software” does not mean “noncommercial.” +On the contrary, a free program must be available for commercial use, +commercial development, and commercial distribution. This policy is +of fundamental importance—without this, free software could not +achieve its aims. +

-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:

+We want to invite everyone to use the GNU system, including businesses +and their workers. That requires allowing commercial use. We hope +that free replacement programs will supplant comparable proprietary +programs, but they can't do that if businesses are forbidden to use +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. +

The freedom to run the program, for any purpose (freedom 0).
The freedom to study how the program works, and adapt it to your needs - (freedom 1). Access to the source code is a precondition for this.
The freedom to redistribute copies so you can help your neighbor - (freedom 2).
The freedom to improve the program, and release your improvements - to the public, so that the whole community benefits - (freedom 3). Access to the source code is a precondition for this.

+Thus, to exclude commercial use, commercial development or commercial +distribution would hobble the free software community and obstruct its +path to success. We must conclude that a program licensed with such +restrictions does not qualify as free 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.

+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. +

+ + +

Clarifying the Boundary Between Free and Nonfree

+ +

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.

+ +

The freedom to run the program as you wish

+ +

+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 +with the developer or any other specific entity. In this freedom, it is +the user's purpose that matters, not the developer's +purpose; you as a user are free to run the program for your purposes, +and if you distribute it to other people, they are then free to run it for +their purposes, but you are not entitled to impose your purposes on them. +

+ +

+The freedom to run the program as you wish means that you are not +forbidden or stopped from making it run. This has nothing to do with what +functionality the program has, whether it is technically capable of +functioning in any given environment, or whether it is useful for any +particular computing activity.

+ +

For example, if the code arbitrarily rejects certain meaningful +inputs—or even fails unconditionally—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.

+ +

“As you wish” includes, optionally, “not at +all” if that is what you wish. So there is no need for a +separate “freedom not to run a program.”

+ +

The freedom to study the source code and make changes

+ +

+In order for freedoms 1 and 3 (the freedom to make changes and the +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 +“source code” is not real source code and does not count +as source code. +

+ +

+Source code is defined as the preferred form of the program for making +changes in. Thus, whatever form a developer changes to develop +the program is the source code of that developer's version. +

+ +

+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 “lockdown,” +or (in its practitioners' perverse terminology) as “secure +boot”—freedom 1 becomes an empty pretense rather than a +practical reality. 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. +

+ +

+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. +

+ +

+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 “freedom to delete the program.” +

+ +

The freedom to redistribute if you wish: basic +requirements

+ +

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 +anyone anywhere. Being free to do these +things means (among other things) that you do not have to ask or pay +for permission to do so. +

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.

+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.

+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 +a copyleft license. However, a +license that requires modified versions to be nonfree does not qualify +as a free license. +

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.

-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 an existing module, such as if it requires you to be -the copyright holder of any code you add, then the license is too -restrictive to qualify as free.

-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.

+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. +

+ +

Copyleft

-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, 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.

-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 substantively block 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 +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. +

+ +

+In the GNU project, we use copyleft to protect the four freedoms +legally for everyone. We believe there are important reasons why +it is better to use +copyleft. However, + +noncopylefted free software is ethical +too. See Categories of Free +Software for a description of how “free software,” +“copylefted software” and other categories of software +relate to each other. +

+ +

Rules about packaging and distribution details

+ +

+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 +name of the modified version, remove a logo, or identify your +modifications as yours. As long as these requirements are not so +burdensome that they effectively hamper you from releasing your +changes, they are acceptable; you're already making other changes to +the program, so you won't have trouble making a few more. +

+ +

+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. An example of such an acceptable rule is one +saying that if you have distributed a +modified version and a previous developer asks for a copy of it, you +must send one. (Note that such a rule still leaves you the choice of +whether to distribute 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, if you have distributed a modified version and a previous -developer asks for a copy of it, you must send one, or that you -identify yourself on your modifications. -

-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.

-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>.

-If you are contemplating writing a new license, please contact the FSF -by writing to that address. The proliferation of different free -software licenses means increased work for users in understanding the -licenses; we may be able to help you find an existing Free Software -license that meets your needs. +are also acceptable.

-If that isn't possible, if you really need a new license, with our -help you can ensure that the license really is a Free Software license -and avoid various practical problems. +A special issue arises when a license requires changing the name by +which the program will be invoked from other programs. That +effectively hampers you from releasing your changed version so that it +can replace the original when invoked by those other programs. This +sort of requirement is acceptable only if there's a suitable aliasing +facility that allows you to specify the original program's name as an +alias for the modified version.

+ +

Export regulations

+ +

+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. Thus, free software licenses +must not require obedience to any nontrivial export regulations as a +condition of exercising any of the essential freedoms.

-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. The word "open" never does that.

- -

Legal considerations

-Return to the GNU Project home page. +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.

-Please send FSF & GNU inquiries to -gnu@gnu.org. -There are also other ways to contact -the FSF. -
-Please send broken links and other corrections (or suggestions) to -webmasters@gnu.org. +A free license may not require compliance with the license of a +nonfree program. Thus, for instance, if a license requires you to +comply with the licenses of “all the programs you use,” in +the case of a user that runs nonfree programs this would require +compliance with the licenses of those nonfree programs; that makes the +license nonfree.

-Please see the -Translations -README for information on coordinating and submitting -translations of this article. +It is acceptable for a free license to specify which jurisdiction's +law applies, or where litigation must be done, or both.

Contract-based licenses

-Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Free -Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA -02110, USA -
-Verbatim copying and distribution of this entire article is -permitted in any medium without royalty provided this notice is -preserved. +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.

-Updated: +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. +

+ +

The Free Software Definition in Practice

+ +

How we interpret these criteria

+ +

+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. +

+ +

Get help with free licenses

+ +

+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>. +

+ +

+If you are contemplating writing a new license, please contact the +Free Software Foundation first by writing to that address. The +proliferation of different free software licenses means increased work +for users in understanding the licenses; we may be able to help you +find an existing free software license that meets your needs. +

+ +

+If that isn't possible, if you really need a new license, with our +help you can ensure that the license really is a free software license +and avoid various practical problems. +

+ +

Use the right words when talking about free software

+ +

+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. +

+ +

+Another group uses 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. +

+ +

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. +

+ +

+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. +

+ +

History

+ +

From time to time we revise this Free Software Definition. Here is +the list of substantive changes, along with links to show exactly what +was changed.

+ +

Version +1.169: Explain 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.
Version +1.165: Clarify that arbitrary annoyances in the code do not +negate freedom 0, and that freedoms 1 and 3 enable users to remove them.
Version +1.153: Clarify that freedom to run the program means nothing stops +you from making it run.
Version +1.141: Clarify which code needs to be free.
Version +1.135: Say each time that freedom 0 is the freedom to run the program +as you wish.
Version +1.134: Freedom 0 is not a matter of the program's functionality.
Version +1.131: A free license may not require compliance with a nonfree license +of another program.
Version +1.129: State explicitly that choice of law and choice of forum +specifications are allowed. (This was always our policy.)
Version +1.122: An export control requirement is a real problem if the +requirement is nontrivial; otherwise it is only a potential problem.
Version +1.118: Clarification: the issue is limits on your right to modify, +not on what modifications you have made. And modifications are not limited +to “improvements”
Version +1.111: Clarify 1.77 by saying that only +retroactive restrictions are unacceptable. The copyright +holders can always grant additional permission for use of the +work by releasing the work in another way in parallel.
Version +1.105: Reflect, in the brief statement of freedom 1, the point +(already stated in version 1.80) that it includes really using your modified +version for your computing.
Version +1.92: Clarify that obfuscated code does not qualify as source code.
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 previous developers on request.

+ +

There are gaps in the version numbers shown above because there are +other changes in this page that do not affect the definition or its +interpretations. For instance, the list does not include changes in +asides, formatting, spelling, punctuation, or other parts of the page. +You can review the complete list of changes to the page through +the cvsweb +interface.

+ +

Footnote

The reason they are numbered 0, 1, 2 and 3 is historical. Around +1990 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 0.

+ +