To take into consideration

Jami is free software for universal communication which respects

freedoms and privacy of its users.
Its main goal is to provide a communication framework and end-user
applications to make audio or video calls, send text messages and make
generic data transfers.

As a free software its sources are licensed under the
GPLv3.

https://git.jami.net/savoirfairelinux/ring-project/wikis/home