Jami

Jami is a free and universal communication platform which preserves the user's privacy and freedoms. It aims to provide all of its users a universal communication tool, free, secure and built on a distributed architecture requiring no authority nor central server to operate.
Jami is completely peer-to-peer and doesn't require a server for relaying data between users.
Jami is a GNU project backed by the Free Software Foundation and licensed under GNU GPLv3 or later.
We use state of the art end-to-end encryption with perfect forward secrecy for all communications and comply with the X.509 standard.