The X Window System, often referred to merely as X, is a complete, cross-platform and free client-server system for managing graphical user interfaces (GUIs) on single computers and on networks of computers. It is one of the most powerful and useful software packages for Linux and other Unix-like operating systems; however, it is a very large and complex system, with the same order of complexity as an operating system itself.
The Open Group is an industry consortium that was formed in 1996 by a merger of the Open Software Foundation (OSF) and X/Open Company, Ltd (X/Open) for the purpose of establishing standards in software engineering. It is best known for its publication of the Single UNIX Specification paper and as the owner of the UNIX trademark. The Open Group acquired stewardship of X in mid-1997 from the X Consortium, a non-profit vendor group which had been formed in 1988 to direct the future development of X while taking into consideration both commercial and educational interests.
In early 1998 the Open Group released X11R6.4, which was a further revision to X11R6, the last major version of X. However, this release was accompanied by a change in licensing terms that were unacceptable to the developers of a number of operating systems. In response, in the latter part of the same year, the Open Group relicensed X11R6.4 under the same terms as its earlier, uncontroversial license (i.e., the widely used MIT License)1.
X.Org provides free implementations of X that are finished products, not merely as bases upon which vendors can build finished products. The actual development work is being done as part of the freedesktop.org community. freedesktop.org is a project that was begun in 2000 for for the purpose of improving the interoperability and shared base technology for desktop environments for X on Unix-like operating systems.
The X.Org Foundation2 was established from X.Org in January 2005 as the consortium holding the stewardship for the development of X. This marked a radical shift in the governance of X: whereas the stewards of X since 1988 (including X.Org) had been vendor organizations, the Foundation was organized as a non-profit scientific charity under U.S. tax code. It is led by software developers, and it utilizes the open source development model, which relies on outside involvement. Membership is available to individuals, and corporate membership is in the form of sponsorship.
In December 2005 the X.Org Foundation officially released X11R6.9 and X11R7.0. The latter was the first major version release of the X in more than a decade, and it is the first release of the complete modularized and autotooled source code base for X. X11R6.9 contains identical features and uses the same source code, but it employs the traditional imake build system. Autotools are the set of GNU tools (including autoconf, automake, autoheader and libtool) that configure the source code packages for a particular computer system.
The most common X variant on Unix-like operating systems was formerly XFree86. However, because the XFree86 project implemented an unpopular change in licensing in February 20043, X.Org (and now X.Org Foundation) has become the main branch of X development, and its implementations of X are expected to be included in most future Linux distributions.
2The X.Org Foundation's home page is http://www.x.org/.
3According to its critics, this change made it incompatible with the GPL (the GNU General Public License), the most widely used free software license. For more information on this controversy, see XFree86 Definition, The Linux Information Project, January 2005.
Created January 28, 2006.