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tine Groupware vs Citadel: catalog facts
tine Groupware	Citadel
Free Open-source software; the research does not detail any paid offerings.	Free Free and open source under the GNU GPL, with no paid edition.
Web, Self-hosted	Web, Self-hosted
Email, calendar, contacts and tasks in one platform Resource planning for shared appointments	Mail, calendar, contacts, forums, wiki and chat in one server Consistent rooms-based structure across features
Website and documentation mostly in German Aimed at organisations rather than individual users	The rooms metaphor differs from conventional mail servers Requires running and maintaining your own server
Self-hosted	Self-hosted
Open source	Open source
License not stated	License: GPL
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.