Zulip
A good starting point for most companies
A team chat app in which conversations are organised into threads.
- Licence
- Apache 2.0
- Language
- interface in Polish
- On a self-hosted server, free mobile push notifications cover up to 10 users. A larger team needs a paid plan from the vendor or, if it qualifies, the Community plan.
Our assessment: All the code is open, and the only significant cost for a larger team is the mobile notification plan, known before deployment.