Mumble was the first and is the most successful and wide spread free and open source software for VoIP. It was the first VoIP software to provide low-latency audio suitable for gaming, and at the same time was a pioneer in high audio quality at the same time. The in-game overlay shows users and who is talking in-game.
- Free open source software, you can easily host your own server.
- Open source chat and audio call service, but could use a face lift.
- Opensource and easy-to-create servers. However, you have to host the servers as mumble doesn't do it themselves.