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 Screenshot of citadel groupware 2011 | |
| Developer(s) | citadel |
|---|---|
| Initial release | Before 1988; 37 years ago (1988) |
| Stable release | 997[1]  / 29 January 2024 |
| Repository | |
| Written in | C |
| Operating system | Unix,Linux |
| Type | Groupware |
| License | 2007:GPL-3.0-only[2][3][4][5] 2006:GPL-2.0-only[6] 1998:GPL-2.0-or-later[7] |
| Website | citadel |
Citadel (originally referred to as "Citadel/UX" to disambiguate it from other implementations) is a collaboration suite (messaging and groupware) that is directly descended from theCitadel family of programs which became popular in the 1980s and 1990s as abulletin board system platform. It is designed to run on open source operating systems such asLinux orBSD. Although it is being used for many bulletin board systems, in 1998 the developers began to expand its functionality to a general purposegroupware platform.
In order to modernize the Citadel platform for theInternet, the Citadel developers added functionality such as shared calendars, instant messaging, and built-in implementations of Internet protocols such asSMTP,IMAP,Sieve,POP3, GroupDAV andXMPP. All protocols offerOpenSSL encryption for additional security.[8]
Users of Citadel systems also have available to them a web-based user interface which employsAjax style functionality to allow application-like interaction with the system.[citation needed]
Citadel uses theBerkeley DB database for all of its data stores, including the message base.[citation needed]
Citadel becamefree and open-source software subject to the terms of theGPL-2.0-or-later license in 1998.[7][9] In 2006 Citadel wasrelicensed to theGPL-2.0-only license.[6] In 2007 Citadel was relicensed again to theGPL-3.0-only license.[5][10]
The developers of the Citadel messaging and collaboration system are pleased to announce that we are now releasing all of our software under version 3 of the GNU General Public License.
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