Open core. Source under AGPLv3 (OSI) or a commercial licence; compiled binaries MIT, admin tools Apache 2.0; Enterprise parts licensed separately Read from the LICENSE file.
GitHub says
NOASSERTION (GitHub could not match a single license, which is why we read the file)
Self-host difficulty
unratedNo docker-compose file at the repository root, so we do not score it.
Activity
★ 39,565 stars · last push 2026-11-10 · checked 2026-11-10
"Mattermost is an open source platform for secure collaboration across the entire software development lifecycle.."
Self-host vs Slack
Self-hosting saves about $120 a year for 20 seats: SaaS $1,740 vs self-host $1,620 (server $144, backups $36, admin time $1,440). Break-even at about 19 seats at these numbers.
Admin hours start from our guess for difficulty unrated and are yours to edit. Slack price: $7.25 per user per month (Pro plan, billed annually). Pro $7.25/user/mo billed annually ($8.75 monthly); Business+ $15/user/mo billed annually ($18 monthly). Source: vendor pricing page, checked 2026-11-10.
