Free and open-source software (FOSS) is software that is distributed in a manner that allows its users to run the software for any purpose, to redistribute copies of it, and to examine, study, and modify, the source code. FOSS is also a loosely associated movement of multiple organizations, foundations, communities and individuals who share basic philosophical perspectives and collaborate practically, but might diverge in detail questions.

The historical precursor to this was the hobbyist and academic public domain software ecosystem of the 1960s to 1980s. The FOSS movement's "free" part originates from Richard Matthew Stallman, who noted the lost freedom to users on the decline of the public domain ecosystem and the growth of a copyrighted proprietary software ecosystem. In response, as a hack of the copyright system, he created the GPL, a protective copyleft license, aiming for the creation of a complete and free operating system — GNU. Shortly after, the BSDs (FreeBSD, OpenBSD, NetBSD) brought an alternative FOSS approach to the table: the more public domain–like permissive licenses. Other noteworthy FOSS organizations from this time include the Apache Foundation (Apache Server), GNOME, Debian, Mozilla Foundation (Firefox), with their own ideas: The Free Software Definition, Debian Free Software Guidelines, The Open Source Definition, and more. At the end of the 1990s, in the context of the dot-com bubble and web 2.0, the Open-Source movement (with Eric S. Raymond, Bruce Perens, Tim O'Reilly and others) gave important impulses to FOSS with the achieved open sourcing of Netscape's browser as Firefox and Sun Microsystems' office suite, OpenOffice.org. The incorporation of Linus Torvalds' Linux kernel in FOSS OS paved the way to broad mainstream recognition and acceptance of FOSS in the IT domain and among the general public. In the 2010s GitHub's openness and collaboration encouraging software repository cloud service brought FOSS software development & maintenance methodologies to mainstream software development.The FOSS movement inspired the creation of other movements, such as open access, open hardware, open content, free culture, open standards, and many more.

The GNU Project (/ɡnuː/ ^ⓘ) is a free software, mass collaboration project announced by Richard Stallman on September 27, 1983. Its goal is to give computer users freedom and control in their use of their computers and computing devices by collaboratively developing and publishing software that gives everyone the rights to freely run the software, copy and distribute it, study it, and modify it. GNU software grants these rights in its license.

In order to ensure that the entire software of a computer grants its users all freedom rights (use, share, study, modify), even the most fundamental and important part, the operating system (including all its numerous utility programs) needed to be free software. Stallman decided to call this operating system GNU (a recursive acronym meaning "GNU's not Unix!"), basing its design on that of Unix, a proprietary operating system. According to its manifesto, the founding goal of the project was to build a free operating system, and if possible, "everything useful that normally comes with a Unix system so that one could get along without any software that is not free." Development was initiated in January 1984. In 1991, the Linux kernel appeared, developed outside the GNU project by Linus Torvalds, and in December 1992 it was made available under version 2 of the GNU General Public License. Combined with the operating system utilities already developed by the GNU project, it allowed for the first operating system that was free software, commonly known as Linux.

The project's current work includes software development, awareness building, political campaigning, and sharing of new material. (Full article...)

Although there was free software before, in 1983 Richard Stallman launched the free software movement and founded the Free Software Foundation to promote the movement and to publish its own definition of free software. Others have published alternative definitions of free software, including the Debian Free Software Guidelines and the Berkeley Software Distribution-based operating system communities.

In 1998, Bruce Perens and Eric S. Raymond began a campaign to market open-source software and founded the Open Source Initiative, which espoused different goals and a different philosophy from Stallman's.

The following operating systems are released under free software licenses:

Impediments and challenges

Digital Millennium Copyright Act · Digital rights management · Tivoization · Software patents and free software · Trusted Computing · Proprietary software · SCO-Linux controversies · Binary blobs

Adoption issues

OpenDocument format · Vendor lock-in · GLX · Free standards · Free software adoption cases

About licences

Free software licences · Copyleft · List of FSF-approved software licenses

Common licences

GNU General Public License · GNU Lesser General Public License · GNU Affero General Public License · IBM Public License · Mozilla Public License · Permissive free software licences

History

...of free software · Free software movement · Timeline of free and open-source software

Groupings of software

Comparison of free software for audio · List of open-source video games

Naming issues

GNU/Linux naming controversy · Alternative terms for free software · Naming conflict between Debian and Mozilla

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