Open source software, free software, free and open source software (FOSS), free, libre and open source software (FLOSS) and sometimes libre software are all names for software whose source code is available, and can be freely used for any purpose, and be modified and redistributed in either the original or modified form. Despite that, open source software is often copyrighted and may be restricted in some respects. For example, wikipedia:copyleft licences (such as the LGPL require that modifications to the code be distributed under the same license.
There are several definitions for what constitutes open source software:
- The Free Software Definition which is maintained by the Free Software Foundation.
- The Open Source Definition which is maintained by the the open-source initiative
- The Debian Free Software Guidelines which provided the basis for the Open Source definition.
Most licences and especially most packages are distributed under all of them.