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'''Free software''', '''software libre''' or '''libre software''' is [[software]] that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with minimal restrictions only to ensure that further recipients can also do these things and that manufacturers of consumer-facing hardware allow user modifications to their hardware. Free software is available gratis (free of charge) in most cases.
In practice, for software to be distributed as free software, the human-readable form of the program (the [[source code]]) must be made available to the recipient along with a notice granting the above permissions. Such a notice either is a "[[free software license]]", or a notice that the source code is released into the public domain.
The free software movement was conceived in 1983 by Richard Stallman to satisfy the need for and to give the benefit of "software freedom" to computer users. The Free Software Foundation was founded in 1985 to provide the organizational structure which Stallman correctly foresaw would be necessary to advance his Free Software ideas.
From 1998 onward, alternative terms for free software came into use. The most common are "software libre", "[[free and open source software]]" ("FOSS") and "free, libre and open source software" ("FLOSS"). The "Software Freedom Law Center" was founded in 2005 to protect and advance FLOSS The antonym of free software is "[[proprietary software]]" or "non-free software". Commercial software may be either free software or proprietary software, contrary to a popular misconception that "commercial software" is a synonym for "proprietary software". (An example of commercial free software is Red Hat Linux.)
Free software, which may or may not be distributed free of charge, is distinct from "[[freeware]]" which, by definition, does not require payment for use. The authors or copyright holders of freeware may retain all rights to the software; it is not necessarily permissible to reverse engineering, modify, or redistribute freeware.
In the late 90s, other groups published their own definitions which describe an almost identical set of software. The most notable are Debian Free Software Guidelines published in 1997, and the Open Source Definition, published in 1998.
The BSD-based operating systems, such as [[FreeBSD]], [[OpenBSD]], and [[NetBSD]], do not have their own formal definitions of free software. Users of these systems generally find the same set of software to be acceptable, but sometimes see copyleft as restrictive. They generally advocate [[permissive free software licenses]], which allow others to make software based on their source code, and then release the modified result as proprietary software. Their view is that this permissive approach is more free. The Kerberos (protocol), X.org, and Apache License software licenses are substantially similar in intent and implementation. All of these software packages originated in academic institutions interested in wide technology transfer University of California, MIT, and University of Illinois at Urbana-Champaign.
== Examples of free software ==
== Security and reliability ==
There is debate over the [[computer security|security]] of free software in comparison to proprietary software, with a major issue being [[security through obscurity]]. A popular quantitative test in computer security is to use relative counting of known unpatched security flaws. Generally, users of this method advise avoiding products which lack fixes for known security flaws, at least until a fix is available.
Free software advocates say that this method is biased by counting more vulnerabilities for the free software, since its source code is accessible and its community is more forthcoming about what problems exist,
== Commercial viability and adoption==
Free software played a part in the development of the Internet, the World Wide Web and the infrastructure of [[dot-com companies]].
Under the free software business model, free software vendors may charge a fee for distribution and offer pay support and software customization services. Proprietary software uses a different business model, where a customer of the proprietary software pays a fee for a license to use the software. This license may grant the customer the ability to configure some or no parts of the software themselves. Often some level of support is included in the purchase of proprietary software, but additional support services (especially for enterprise applications) are usually available for an additional fee. Some proprietary software vendors will also customize software for a fee.
=== Binary blobs ===
In 2006, [[OpenBSD]] started the first campaign against the use of [[binary blobs]], in [[kernel (computer science)|kernels]]. Blobs are usually freely distributable [[device driver]]sdrivers for hardware from vendors that do not reveal driver source code to users or developers. This restricts the users' freedom to effectively modify the software and distribute modified versions. Also, since the blobs are undocumented and may have [[computer bug|bugs]], they pose a security risk to any [[operating system]] whose kernel includes them. The proclaimed aim of the campaign against blobs is to collect hardware documentation that allows developers to write free software drivers for that hardware, ultimately enabling all free operating systems to become or remain blob-free.
The issue of binary blobs in the [[Linux kernel]] and other device drivers motivated some developers in Ireland to launch [[gNewSense]], a GNU/Linux distribution with all the binary blobs removed. The project received support from the [[Free Software Foundation]].
=== BitKeeper ===
[[Larry McVoy]] invited high-profile free software projects to use his proprietary [[versioning system]], [[BitKeeper]], free of charge, in order to attract paying users. In 2002, Linux coordinator [[Linus Torvalds]] decided to use BitKeeper to develop the [[Linux kernel]], a free software project, claiming no free software alternative met his needs. This controversial decision drew criticism from several sources, including the Free Software Foundation's founder Richard Stallman.
Following the apparent [[reverse engineering]] of BitKeeper's protocols, McVoy withdrew permission for gratis use by free software projects, leading the Linux kernel community to develop a free software replacement called [[Git (software)|Git]].
=== Patent deals ===
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