Zulip

Zulip is an open-source team chat app with topic-based threading that combines email-style organization with real-time messaging. It can be self-hosted on Linux/Docker or used via Zulip Cloud, with web, desktop and mobile apps.

• Open-source alternative to: Slack, Microsoft Teams
• Licence: Apache-2.0 (Permissive open source)
• Website: https://zulip.com/
• Source code: https://github.com/zulip/zulip
• GitHub stars: 26145, forks: 10514
• Topics: team chat, messaging, collaboration, self-hosted, communication, apache, chat, electron, foss, free, javascript, python