We’re a YC-backed indie video game company releasing an open source alternative to Slack.
It’s called “Mattermost” and it’s the team communication service our company’s run on since last year. Like Slack, you can send messages and files across channels, get notifications on unreads and mentions, and search history–all from your PC or smartphone.
Unlike Slack, Mattermost is open source. You can download the code, run it on your own servers, and modify it as you wish.
This was bound to happen sooner or later. Appears to be written in Go.