We wanted to have a simple working solution for audio calls.
- Jitsi - https://jitsi.org/ technically superbe but the UI is quite aweful in Java
- Ekiga - http://www.ekiga.org/ maybe a bit dead
- Ring - https://ring.cx/ growing fast, GUN project, mixing SIP+BHT+blockchain
- Wazo - http://wazo.community/ early stage, already usable, growing fast