Mattermost – Open Source Slack Alternative
Mattermost is an open source, self-hosted Slack-alternative that offers modern communication from behind your firewall. We built it so users have a practical option for avoiding lock-in from proprietary SaaS services. Mattermost is designed to be Slack-compatible (but not Slack-limited). That means we help users move over from Slack, but without limiting Mattermost to another product’s feature set.
Mattermost infrastructure is built for IT admins who want to quickly stand up a self-hosted alternative to Slack that’s easy to install, deploy, manage and scale. Mattermost includes a web-based System Console for managing instance level configuration. To simplify licensing, they have responded to community feedback and the compiled version of Mattermost v1.0 is now under the MIT open source license (instead of Apache-AGPL).
License: MIT License