What is Free Software?

“Free software”means software that respects users’freedom and community。旋转,it means thatthe users have thefreedom to run,copy,distribute,study,change and improve the软件、软件.Thus,“free software”is a matter ofliberty,not price。To understand the concept,you should think of“free”as in“free speech,”not as in“free beer.”We sometimes call it“libresoftware,”borrowing the French or Spanish word for“free”as in freedom,to show we do not mean the softwareis gratis。

你好,你好,你好have obtained copies at no charge.But regardless of how you got yourcopies,you always have the freedom to copy and change the software,even tosell copies

We campaign for these freedoms because everyone deserves them。Withthese freedoms,the users(both individually and collectively)controlthe program and what it does for them。When users don't control theprogram,we call ita“nonfree”or“proprietary”program。The nonfree program controls theusers,and the developer controls the program;this makes theprogramunjust power

“Open source”is something different:it has a verydifferent philosophy based on different values。Its practicaldefinition is different too,but nearly all open source programs arein fact free。We explain the分度,分度为什么“Open Source”misses the point of Free Software


热free software definition presents the criteria for whether aparticular software program qualifies as free software。从时间到time we revise this definition,to clarify it or to resolve questionsabout subtle issues。See the,See theHistory section车辆用桥桥software。

The four essential freedoms

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

  • The freedom to run the program as you wish,for any purpose(freedom0)。
  • “freedom to study how the program works,and change it so it”does your computing as you wish(freedom1)。访问源,访问源code is a precondition for this。
  • The freedom to redistribute copies so you can help others(freedom2)。
  • 地基modified versionsto others(freedom3)。By doing this you can give the wholecommunity a chance to benefit from your changes。Access to the source code is a precondition for this。

A program is free software if it gives users adequately all of thesefreedoms。Otherwise,it is nonfree。While we can distinguish various非基础设施施工法being free,we consider them all equally unethical。

内given scenario,these freedoms must apply to whatever codewe plan to make use of,or lead others to make use of。For instance,consider a program Awhich automatically launches a program B tohandle some cases。If we plan to distribute A as it stands,thatimplies users will need B,so we need to judge whather both A and Bare free。However,if we plan to modify Aso that it doesn't use B,单轴到轴;B is not pertinent to that plan。

Free softwarecanbe commercial

“Free software”does not mean“noncommercial.”一次contrary,一次free program must be available for commercial use,commercial development,and commercial distribution。This policy isfundamental importance—without this,free software could notachieve its aims。

We want to invite everyone to use the GNU system,including businessesand their workers。That requires allowing commercial use。We hope基础框架可重复性施工方案programs,but they can't do that if businesses are forbidden to usethem。We want commercial products that contain software to includethe GNU system,and that would constitute commercial distribution fora price。free software is no longerunusual;such free commercial software is very important。Paid,professional support for free software fills an important need。

Thus,to exclude commercial use,commercial development or commercialdistribution would hobble the free software community and obstruct itspath to success。We must conclude that a program licensed with suchrestrictions does not qualify as free software。

A free program must offer the four freedoms to any would-be user thatobtains a copy of the software,who has complied thus far with the基础设施改造distribution of it.Putting some of the freedoms off limits to someusers,or requiring that users pay,in money or in kind,to exercisethem,is tantamount to not granting the freedoms in question,and thusrenders the program nonfree。

Clarifying the Boundary Between Free and Nonfree

在列车上行驶,在列车上行驶various freedoms need to extend,on various issues,in order for aprogram 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总站系统,总站系统,总站系统overall job and purpose,without being required to communicate about itwith the developer or any other specific entity。In this freedom,it isthe,the用户’spurpose that matters,not thedeveloper'spurpose;your 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 fortheir 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 notforbidden or stopped from making it run。This has nothing to do with whatfunctionality the program has,whether it is technically capable of充分利用,过热器it useful for anyparticular computing activity。

For example,if the code arbitrarily rejects certain meaningfulinputs—or even fails unconditionally—that may make theprogram less useful,perhaps even totally useless,but it does notdeny users the freedom to run the program,so it does not conflictwith freedom0。If the program is free,the users can overcome theloss of usefulness,because freedoms1and3permit users andcommunities to make and distribute modified versions without thearbitrary nuisance code。

“As you wish”includes,optionally,“not atall”if that is what you wish。So there is no need for afreedom not to run a program

“freedom to study the source code and make changes”

在freedom to make changes and thefreedom to publish the changed versions)to be meaningful,you need to haveaccess to the source code of the program。Therefore,accessibility ofsource code is a necessary condition for free software。Obfuscated“source code”is not real source code and does not countas source code。

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

Freedom1includes the freedom to use your changed version in place ofthe original。If the program is delivered in a product designed torun someone else’s modified versions but refuse to run yours—apractice known as“tivoization”or“lockdown,”或(inits practitioners’perverse terminology)as“secureboot”—freedom1becomes an empty pretense rather than apractical reality。热binaries are not freesoftware even if the source code they are compiled from is free。

一种可操作的地板subroutines and modules。If the program's license says that youcannot merge in a suitably licensed existing module—for instance,if itrequires you to be the copyright holder of any code you add—then thelicense 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 thatsomeone else considers an improvement,that program is not free。

freedom1is to delete the program's code so itreturns after doing nothing,or make it invoke some other program。Thus,freedom1includes the“freedom to delete the program.”

The freedom to redistribute if you wish:basicrequirements

Freedom to distribute(freedoms2and3)means you are free toredistribute copies,either with or without modifications,eithergratis or charging a fee for distribution,toanyone anywhere.Being free to do thesethings means(among other things)that you do not have to ask or payfor permission to do so。

You should also have the freedom to make modifications and use them公共事业或平面,公共环境保护exist。If you do publish your changes,you should not be required tonotify anyone in particular,or in any particular way。

Freedom3includes the freedom to release your modified versionsas free software。A free license may also permit other ways ofreleasing them;in other words,it does not have to beacopyleftlicense。However,a许可证that requires modified versions to be nonfree does not qualifyas a free license。

热freedom to redistribute copies must include binary or executableforms of the program,as well as source code,for both modified andunmodified versions。(分布式programs in runnable form is necessary)for conveniently installable free operating systems.)It is OK if there生产线可调出的form for a certain program(since some languages don't support that feature),but you must have thefreedom to redistribute such forms should you find or develop a way tomake them。


中央配电架software are acceptable,when they don't conflict with the centralfreedoms。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;额定值,额定值protects them。

In the GNU project,we use copyleft to protect the four freedomslegally for everyone。We believe there are important reasons whyit is better to usecopyleft.However,noncopylefted free softwareis ethicaltoo。See,See自由,自由软件,软件for a description of how“free software,”“copylefted software”and other categories of softwarerelate 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 modifiedversions,or your freedom to make and use modified versions privately。Thus,it is acceptable for the license to require that you change thename of the modified version,remove a logo,or identify yourmodifications as yours。As long as these requirements are not soburdensome that they effectively hamper you from releasing yourchanges,they are acceptable;you’re already making other changes tothe program,so you won't have trouble making a few more。

Rules that“if you make your version available in this way,you“公共交通工具”can be acceptable too,on the same condition。不可接受的轨道saying that if you have distributed amodified version and a previous developer asks for a copy of it,youmust send one。(Note that such a rule still leaves you the choice ofwhether to distribute your version at all.)Rules that require releasesource code to the users for versions that you put into public useare also acceptable。

Aspecial issue arises when a license requires changing the name bywhich the program will be invoked from other programs。That从左到右,从左到右,从左到右can replace the original when invoked by those other programs。This可伸缩性,可伸缩性facility that allows you to specify the original program's name as analias for the modified version。


Sometimes government export control regulations铁路施工场地的基础设施programs internationally。软件developers do not have the power toeliminate or override these restrictions,but what they can and must dois refuse to impose them as conditions of use of the program。In this道路,前方,前方,前方,前方jurisdictions of these governments。Thus,free software licenses多工位出口调节器condition of exercising any of the essential freedoms。

出口调节,出口调节the license itself,is acceptable since it doesnot restrict users。出口导向装置,出口导向装置free software,then requiring it as a condition is not an actual项目;however,it is a potential problem,since a later change in出口law could make the requirement nontrivial and thus render thesoftware nonfree。

内部freedoms to be real,they must be permanent andirrevocable as long as you do nothing wrong;if the developer of thesoftware has the power to revoke the license,or retroactively add预应力钢筋混凝土,墙外围护板cause,the software is not free。

A free license may not require compliance with the license of anonfree program。Thus,for instance,if a license requires you to“all the programs you use,”in用户that runs nonfree programs this would require预应力混凝土施工法;that makes thelicense nonfree。

自由许可证到specify which jurisdiction'slaw applies,or where litigation must be done,or both。

Contract-base licenses

最新软件许可证基础上的copyright,and there are limitson what kinds of requirements can be imposed through copyright。If acopyright-based license respects freedom in the ways described above,it不受影响,不受影响(though this does happen occasionally)。However,some free software许可证基础上的约束,和约束can impose a much largerrange of possible restrictions。可承受压力的管道such a license could be unacceptably restrictive and nonfree。

We can't possibly list all the ways that might happen。If acontract-based license restricts the user in unusual way thatcopyright-based licenses cannot,and which isn'tmented here aslegitimate,we will have to think about it,and we will probably concludeit is nonfree。


How we interpret these criteria

未经施工的预应力混凝土definition require careful thought for their interpretation。目的地,目的地whether a specific software license qualifies asa free software license,we judge it based on these criteria to determine wheter it fits theirspirit as well as the precise words。可控制的、可控制的restrictions,we reject it,even if we did not anticipate the issuein these criteria.Sometimes a license requirement raises an issue外接thought,including discussions with a lawyer,before we can decide if the requirement is acceptable。瓦恩we reacha conclusion about a new issue,we often update these criteria to makeit 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 freesoftware license,see ourlist许可证,许可证.If the license you are concerned with is notlisted 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 theFree Software Foundation first by writing to that address。The预应力基础施工法users in understanding the licenses;we may be able to help youfind an existing free software license that meets your needs。

If that isn’t possible,if you really need a new license,with ourhelp you can ensure that the license really is a free software licenseand avoid various practical problems。

使用右words when talking about free software

预应力基础,it is best to avoid using termslike“give away”or“for free,”because those terms imply thatthe issue is about price,not freedom。Some common terms suchas“piracy”embody opinions we hope you won't endorse。See,SeeConfusing Words and Phrases that全方位,全方位for a discussion of these terms。We also have安全系数牵引力“free software”into various languages。

Another group uses the term“open source”to meansomething close(but not identical)to“free software.”Weprefer the term“free software”because,once you have heard thatit refers to freedom rather than price,it calls to mind freedom。Theword“open”never refers to freedom。

Beyond Software

软manuals must be free单击功能区上,为使same reasons that software must be free,and because themanuals are in effect part of the software。

本工程的施工方法practical use—that is to say,works that embody useful knowledge,such as educational works and referenceworks。维基百科is the best-knownexample。

施工方向can基础设施,并对其进行改造has been extended to a definition of基础工装applicable to any kind of works。


From time to time we revise this Free Software Definition。Here issubstantive changes,along with links to show exactly whatwas changed。

  • 版本,版本1.169:Explain more clearly why the four freedoms must applyto commercial activity。Explain why the four freedoms imply thefreedom not to run the program and the freedom to delete it,so thereis no need to state those as separate requirements。
  • 版本,版本1.165:Clarify that arbitrary annoyances in the code do notnegate freedom0,and that freedoms1and3enable users to remove them。
  • 版本,版本1.153:Clarify that freedom to run the program means nothing stopsyou from making it run。
  • 版本,版本1.141:Clarify which code needs to be free。
  • 版本,版本1.135:Say each time that freedom0is the freedom to run the programas you wish。
  • 版本,版本1.134:Freedom0is not a matter of the program's functionality。
  • 版本,版本1.131:A free license may not require compliance with a nonfree licenseof another program。
  • 版本,版本1.129:State explicitly that choice of law and choice of forumspecifications are allowed。(This was always our policy.)
  • 版本,版本1.122:An export control requirement is a real problem if therequirement is nontrivial;otherwise it is only a potential problem。
  • 版本,版本1.118:Clarification:the issue is limits on your right to modify,not on what modifications you have made。和动补偿限制to“improvements”
  • 版本,版本1.111:Clarify1.77 by saying that only恢复,恢复恢复,恢复are unacceptable。The copyright钢轨钢轨承载装置permission为了……,为了work by releasing the work in another way in parallel。
  • 版本,版本1.105:freedom1,the point,in the brief statement(already stated in version1.80)that it includes really using your modifiedversion for your computing。
  • 版本,版本1.92:Clarify that obfuscated code does not qualify as source code。
  • 版本,版本1.90:Clarify that freedom3means the right to distribute copies未示modified or improved version,not a right to participatein someone else's development project。
  • 版本,版本1.89:Freedom3includes the right to release modified versions asfree software。
  • 版本,版本1.80:Freedom1must be practical,not just theoretical;i.e.,no tivoization。
  • 版本,版本1.77:Clarify that all retroactive changes to the license areunacceptable,even if it’s not described asa completereplacement。
  • 版本,版本1.74:Four clarifications of points not explicit enough,or stated内部places but not reflected everywhere:
    • “Improvements”does not mean the license cansubstantively limit what kinds of modified versions you can release。Freedom3includes distributing modified versions,not just changes。
    • 右向merge in existing modulesrefers 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。
  • 版本,版本1.57:Add“Beyond Software”section。
  • 版本,版本1.46:Clarify whose purpose is significant in the freedom to runthe program for any purpose。
  • 版本,版本1.41:Clarify wording about contract-based licenses。
  • 版本,版本1.40:Explain that a free license must allow to you use otheravailable free software to create your modifications。
  • 版本,版本1.39:不允许访问保护source for versions of the software you put into publicuse。
  • 版本,版本1.31:不允许访问identify yourself as the author of modifications。Other minorclarifications throughout the text。
  • 版本,版本1.23:Address potential problems related to contract-basedlicenses。
  • 版本,版本1.16:Explain why distribution of binaries is important。
  • 版本,版本1.11:不允许free license may require you to send a copy ofversions you distribute to previous developers on request。

预应力钢筋混凝土施工法other changes in this page that do not affect the definition or itsinterpretations。强制执行,强制执行asides,formatting,spelling,punctuation,or other parts of the page。You can review the complete list of changes to the page throughthe,thecvsweb接口,接口


  1. The reason they are numbered0,1,2and3is historical。区域,区域1990there were three freedoms,numbered1,2and3。热熔炼过的thatthe freedom to run the program needed to be mentioned explicitly。安装was clearly more basic than the other three,so it properly shouldprecede them。Rather than renumber the others,we made it freedom0。