Comment by godelski

For anyone that needs the link: https://github.com/mattermost/mattermost/blob/master/LICENSE...

Also note that they have an enterprise license (/server/enterprise/License): https://github.com/mattermost/mattermost/blob/master/server/...

The README on the enterprise directory also links to a page with more detail (FAQ): https://docs.mattermost.com/product-overview/frequently-aske...