The GPL is the Free Software Foundation's General Public Licence. The GPL is considered the standard open source software licence, and many non-software works are published under the GPL as well. The purpose of this license is to ensure that a work can be freely distributed and modified by anybody, and that no proprietary works can be derived from the original work. Past versions of the GPL have been quite liberal in what they allow an end user or developer to do with software, but have been vague in some definitions. The third version of the license, currently under development, aims to more clearly define and restrict developments such as DRM. This has led to much controversy, and traditional supporters and advocates of the GPL are currently split as to its continued value.
The original GPL was a combination of licences written by Richard Stallman for software he wrote himself. Finding contradictions in some of his licences that made them mutually exclusive, Richard developed a license that satisfied his very strict desire to see software code made publicly available, yet was abstract enough to apply to all the different titles that he sought to protect with it. This had the compound effect of allowing different software titles released under the common licence to share a code base, thus saving valuable programming time and disk space. The first official version of the GPL was released in early 1989. The main innovation of this licence was the requirement that the source code of all GPL'ed software be made freely available. No other licence had addressed this concern at the time, in fact most software then in use went to great lengths to protect and hide its source code. Within two years Stallman realized that his licence could be easily circumvented by those who would slightly change programs released under the GPL. These variants were being released under different licences that neither required the availability of the source nor credited the original author. So version 2 of the GPL included a new clause: any work derived from GPL'ed software must in turn be released under the GPL as well. At the same time as GPL v2 was released, the less restrictive LGPL was introduced for software libraries that would allow for the sharing of code across applications.
While most software titles distributed today are released under proprietary licences, quite a few GPL programs have gained in popularity in the time since the second version of the GPL was released. Foremost among these is the Linux operating system kernel, and most software distributed with it. Probably the most familiar GPL licenced program is the Firefox Internet web browser, which is replacing the proprietary Internet Explorer on most desktop computer systems. While not as popular as Firefox, Open Office is another GPL program that is seeing fast adaptation on home and office desktop PC's. Other common applications of the GPL include the Wikipedia online encyclopedia, and Sun's Java programming language.
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