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.

Wine is a free and open-source compatibility layer to allow application software and computer games developed for Microsoft Windows to run on Unix-like operating systems. Developers can compile Windows applications against WineLib to help port them to Unix-like systems. Wine is predominantly written using black-box testing reverse-engineering, to avoid copyright issues. No code emulation or virtualization occurs. Wine is primarily developed for Linux and macOS.

In a 2007 survey by desktoplinux.com of 38,500 Linux desktop users, 31.5% of respondents reported using Wine to run Windows applications. This plurality was larger than all x86 virtualization programs combined, and larger than the 27.9% who reported not running Windows applications. (Full article...)

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