MattermostCoordinate work through channels, messages and shared files.
Source published on GitHub under a custom/non-standard licence (GitHub shows no standard SPDX id); check terms for commercial use.
Notes, tasks & docs
Zulip
Free optionOpen sourceBrowser
Organise team conversations into streams and focused topic threads.
What you can use it for
Organise team conversations into streams and focused topic threads.
- Covers the core everyday task of Slack: team chat.
- 26.1k GitHub stars; last commit 2026-10-15.
Workflow coverage and comparison notes
Power internal communication, topic-based discussions and unlimited searchable team chat history with Zulip instead of Chanty Business seat tiers.
Before you switch
Zulip Cloud free plan has limits; self-host free
Alternatives to these paid apps
Each comparison covers the workflow described above, rather than every paid feature.
More for the same workflow
See alternatives →Mattermost