Definition Citadel Software
Explanation: Citadel is software for running a Bulletin Board System. The first Citadel came online in 1980 with a single 300 baud modem, and some versions of the software, supporting thousands of simultaneous users, are still in use today. Citadel development has always been collaborative with a strong push to keep the source code in the public domain. This makes Citadel one of the oldest surviving FOSS projects.
Other definitions in programming such as Citadel Software in Dictionary C.