Free software, software libre, or libre software is computer software that gives users the freedom to run the software for any purpose as well as to study, modify, and distribute the original software and the adapted versions. The rights to study and modify free software imply unfettered access to its source code. For computer programs which are covered by copyright law this is achieved with a software license where the author grants users the aforementioned freedoms. Software which is not covered by copyright law, such as software in the public domain can also be free if the source code is in the public domain (or otherwise available without restrictions). Other legal and technical aspects such as software patents and DRM may impede users from exercising these rights, and thus prevent software from being free. Free software may be developed collaboratively by volunteer computer programmers or by corporations; as part of a commercial activity or not. Free software is primarily a matter of liberty, not price: users, individually or collectively, are free to do whatever they want with it – this includes the freedom to redistribute the software free-of-charge, or to sell it (or related services such as support or warranty) for profit. Free software thus differs from proprietary software (such as Microsoft Windows), which to varying degrees prevents users from studying, modifying and sharing the software. Free software is also distinct from freeware, which is simply a category of proprietary software which does not require payment for use. Proprietary software (including freeware) uses restrictive software licences or user agreements and usually does not provide access to the source code. Users are thus prevented from modifying the software, and this results in the user becoming dependent on software companies to provide updates and support (vendor lock-in). Users can also not necessarily reverse engineer, modify, or redistribute proprietary software. The term “free software” was coined in 1985 by Richard Stallman when launching the GNU project – a collaborative effort to create a freedom-respecting operating system – and the Free Software Foundation (FSF). The FSF’s Free Software Definition states that users of free software are “free” because they do not need to ask for any permission.