Mattermost
Self-managed chat with published source.
COMPARE AND CHECK
Open-source Slack alternatives you can self-manage
Short answer: Open-source Slack alternatives you can self-manage. Put the current file, the decision and the next owner in one channel. Basic is 9 USD per paid account a month, or 86 USD a year, with 25 GiB. The trial is 3 days. The iPhone and iPad app is coming soon. The encryption scope is on the security page.
Open-source Slack alternatives: Mattermost, Rocket.Chat, Element and Zulip. Confirm each license. BusyVault is not listed as open source.
Short answer. Open-source Slack alternatives on this page are Mattermost, Rocket.Chat, Element and Zulip. Each publishes source and a way to run more than a rented seat. Confirm the current license on the vendor site before you install. BusyVault is not in this list. We do not describe BusyVault as open source.
Open-source Slack alternatives and the work that stays with you
| Project | What is public | What you still operate |
|---|---|---|
| Mattermost | Source and a self-managed option. | Host, backups, upgrades. |
| Rocket.Chat | Source plus community and commercial editions. | Which edition your deploy is allowed to run. |
| Element | A Matrix client and a public network. | A homeserver, if you need one. |
| Zulip | Source and a cloud tier. | Topics, hosting and the current plan limit. |
BusyVault is not listed as open source
BusyVault's public offer is a hosted account: Basic 9 USD a month or 86 USD a year, Pro 30 USD or 288 USD, 25 GiB or 100 GiB, extra storage 0.03 USD per GiB. Putting that product in an open-source ranking would invent a license. If you need the source and the server, use the four projects above and read their licenses.
Tools on this list
Rocket.Chat
Community and commercial editions. Confirm the license.
Element
Matrix client. Federation and a homeserver are separate choices.
Zulip
Topic-based chat with published source.
QUESTIONS
Questions about open-source Slack alternatives
Is open source the same as free?
No. You can still pay for hosting, a commercial edition or an operator. Read the license.
Why only four names?
These are the projects this site already discusses and whose homepages we link. A longer list without a checked license would be a logo dump.
Does BusyVault offer the source?
Not on this page. Do not treat the hosted app as an open-source Slack alternative.
What to write down before you switch
Read “Open-source Slack alternatives you can self-manage” as a buying note for one job, not as a score. Name the file you would actually send, the history you still need to search, and who pays for each account. BusyVault is the hosted app for that job. Other products stay on this page only where the comparison says who runs the server or what one upload allows. There is no star rating and no laboratory winner. Keep the quote you were sent beside any public price printed here.
Files, history and the next owner
On Open-source Slack alternatives you can self-manage, keep the file next to the sentence that approved it. Slack documents a 1 GB cap on one upload and, on the Free plan, 90 days of visible history. Those two limits are the public facts this site already cites.
BusyVault bills storage per paid account: 25 GiB on Basic and 100 GiB on Pro. Extra storage is 0.03 USD per GiB a month after you confirm the charge. Basic is 9 USD a month or 86 USD a year. Pro is 30 USD a month or 288 USD a year. One subscription does not cover the team.
The trial is 3 days and 10 GiB. Use it to upload a real file and to search for a decision, not to announce a company-wide move. If the file does not fit or the old decision cannot be found, say so in the channel before you promise the room is the archive.
Where the app runs
BusyVault runs in the browser and can be installed from Chrome or Edge on Windows, macOS and Linux. The Android app is on Google Play and uses the same account. The iPhone and iPad app is coming soon. Enterprise customers can run BusyVault on their own servers under a separate contract. There is no public installer on this site for that path. This page does not claim SOC 2, ISO 27001 or HIPAA.
A check you can finish this week
For Open-source Slack alternatives you can self-manage, finish four lines and stop. Line one is the project name. Line two is the channel name. Line three is where the current file lives. Line four is the next owner. Add one rule for meetings: what must be decided live, and what must be written down the same day.
Ask someone who was not on the call to find the file without help. If they open the right channel first, the structure works. If they search three threads and still ask which version is current, move the file to the channel and leave a pointer. Owners and administrators can export a BusyVault backup from workspace or channel settings. After a restore, check the text, the file references and who can open them. Keep the original files until that check passes. Product questions go to the address on the support page.
Count the operator, not only the license
Open source Slack alternatives such as Mattermost and Rocket.Chat let you run the service. That is the point when a vendor cloud is not allowed. It is also a payroll cost: backups, upgrades and who is on call. BusyVault on this site is the hosted app, not a self-host guide. Do not list it as open source. Use the shortlist when the question is the project file, and this page when the question is who holds the server.
YOUR NEXT PROJECT
Less searching. More work done together.
Start your 3-day trialTry it with a real project. Then choose Basic or Pro.