| Revision as of 23:17, 5 September 2026 by OpenWiki (Imported from the OpenWiki starter corpus) | Revision as of 00:19, 6 September 2026 by OpenWiki (Updated from the starter corpus) | ||
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| == Copyleft == | == Copyleft == | ||
| − | Free licences divide into two families. '''Permissive''' licences, such as the MIT and BSD licences, allow redistribution under any terms, including proprietary ones. '''Copyleft''' licences, of which the GNU General Public License is the best known, require that derivative works carry the same | + | Free licences divide into two families. '''Permissive''' licences, such as the MIT and BSD licences, allow redistribution under any terms, including proprietary ones. '''Copyleft''' licences, of which the GNU General Public License is the best known, require that derivative works carry the same licence, using copyright law to compel openness rather than to restrict copying. |
| The practical difference shows up when a company builds a product on free code. Under a permissive licence it may keep its modifications private; under a strong copyleft licence it must publish them if it distributes the result. | The practical difference shows up when a company builds a product on free code. Under a permissive licence it may keep its modifications private; under a strong copyleft licence it must publish them if it distributes the result. | ||
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| Sharing source code was ordinary practice in early computing, when software was supplied with hardware and users were expected to adapt it. As software became a product sold separately in the late 1970s, source code was withheld and licences began to forbid modification. | Sharing source code was ordinary practice in early computing, when software was supplied with hardware and users were expected to adapt it. As software became a product sold separately in the late 1970s, source code was withheld and licences began to forbid modification. | ||
| − | Stallman began the GNU Project in 1983 to build a complete free operating system, and wrote the GNU General Public License in 1989. By the early 1990s GNU had produced most of a system | + | Stallman began the GNU Project in 1983 to build a complete free operating system, and wrote the GNU General Public License in 1989. By the early 1990s GNU had produced most of a system (compiler, editor, shell, libraries) but not a working kernel. In 1991 Linus Torvalds released the Linux kernel and licensed it under the GPL; combined with the GNU tools, it completed the system. |
| In 1998 part of the community adopted the term '''open source''', arguing that "free" was ambiguous and that a case emphasising development quality and cost would appeal to businesses more than one emphasising liberty. The licences the two movements accept overlap almost entirely; the disagreement is about which argument to lead with. | In 1998 part of the community adopted the term '''open source''', arguing that "free" was ambiguous and that a case emphasising development quality and cost would appeal to businesses more than one emphasising liberty. The licences the two movements accept overlap almost entirely; the disagreement is about which argument to lead with. | ||
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