Digistorm

Tracim

Threads, files and pages with status and full history. All in the same place.

Citadel

Groupware including email, calendar/scheduling, address books, forums, mailing lists, IM, wiki and blog engines, RSS aggregation and more. (Source Code) GPL-3.0 C/Docker/Shell

Colanode

Collaboration suite with real-time messaging, rich text pages, file management, and dynamic databases - built for offline work (alternative to Slack, Notion). (Source Code) Apache-2.0 K8S/Docker

Zimbra Collaboration

Email, calendar, collaboration server with Web interface and lots of integrations. (Source Code) GPL-2.0/CPAL-1.0 Java