Zimbra Collaboration

Tracim

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

Openmeetings

Video conferencing, instant messaging, whiteboard, collaborative document editing and other groupware tools using API functions of the Red5 Streaming Server for Remoting and Streaming. (Source Code) Apache-2.0 Java

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