Mattermost

Mattermost is an open-core, self-hosted team collaboration platform with channels, threads, direct messages, file sharing, searchable history and calls, deployable on your own infrastructure including private-cloud and air-gapped environments on web, desktop and mobile.

• Open-source alternative to: Slack, Microsoft Teams
• Licence: NOASSERTION (Custom or unrecognized license)
• Website: https://mattermost.com/
• Source code: https://github.com/mattermost/mattermost
• GitHub stars: 39511, forks: 9089
• Topics: team chat, messaging, collaboration, self-hosted, communication, golang, hacktoberfest, mattermost, monorepo, react, react-native