Mattermost

Mattermost serves as a self-contained collaboration platform, providing tools for chat, workflow automation, voice calling, screen sharing, and AI integration. Its code licensing under the AGPL is somewhat unclear and does not completely align with the Open Source Definition.

As an open-source alternative to proprietary SaaS messaging platforms, Mattermost consolidates team communication into a single, searchable, and universally accessible location. It is developed using Golang and React and operates as a production-grade Linux binary under an MIT license, compatible with both MySQL and Postgres databases.

Mattermost is compatible with Slack but not limited to its features. It matches and expands on Slack's capabilities, supporting a broader range of incoming and outgoing webhook integrations, including compatibility with pre-existing Slack integrations. Users can import data from existing Slack teams, including users, public channel history, and theme setting colors. Mattermost can be accessed through iOS or Android mobile devices, desktop apps on Windows, Linux, and Mac, in addition to its web version. It is designed for easy deployment, management, and upgrading, running as a Linux binary, Docker image, among other formats. A vibrant community supports Mattermost, offering numerous community integrations and applications, such as Jira, IRC, XMPP, Hubot, Giphy, Jenkins, GitLab, Trac, Redmine, SVN, RSS/Atom and more. Users can also develop and share their own apps using Mattermost APIs and drivers.