GNU (GNU's Not Unix)
- GNU operating system: A Unix-like operating system for computers. GNU is the operating system used by Linux. See http://www.gnu.org/gnu/linux-and-gnu.html.
- GNU licence/copyright: A series of licences designed for ensuring the non-restrictive distribution of software and documentation. See GNU Public Licence (GPL) and Free Documentation Licence (FDL).
"Free" in GNU-speak does not necessarily mean "gratis". GNU-based and/or licenced software can be sold. Rather it means "open". GNU software and documentation can be modified, redistributed, sold, or given away on condition that subsequent users receive the same right to modify, repackage, redistribute, sell, or give the software away as well.