The idea is very similar to the copyleft concept of the Free Software Foundation. Open Source is the result of a long-time movement toward software that is developed and improved by a group of volunteers cooperating together on a network. Many parts of the UNIX operating system were developed this way, including today's most popular version, Linux. Linux uses applications from the GNU project, which was guided by Richard Stallman and the Free Software Foundation. The Open Source Definition, spearheaded by Eric Raymond (editor of The New Hacker's Dictionary), is an effort to provide a branded model or guideline for this kind of software distribution and redistribution. The OSI considers the existing software distribution licenses used by GNU, BSD (a widely-distributed version of UNIX), X Consortium, and Artistic to be conformant with the Open Source Definition.
Prior to its acquisition by AOL, Netscape, in an effort to stay viable in its browser competition with Microsoft, made its browser source code (codenamed Mozilla) freely available, encouraging hackers to improve it. Possible enhancements will presumably be incorporated into future versions. The open source movement has gained momentum in the latter half of 1998 as commercial enterprises have begun to consider Linux as an open alternative to Windows 9x/NT.