Berty Messenger is a messaging app built on the Wesh Network protocol, which the project describes as decentralised and serverless. Devices exchange messages peer to peer, although the project's code includes a rendezvous point server that helps devices find each other. The software is open source, licensed under Apache 2.0 or MIT at the user's choice. The documentation states that the project is still under active development and should not yet be used for important data.
Berty Technologies, the organisation behind the project, describes itself as a non-profit based in Paris, France. Because no vendor-operated server stores messages, hosting becomes a question of who runs any relay or rendezvous server, and the sources consulted do not name that operator. The code can be reviewed and run on infrastructure the user chooses. For a European organisation this is a self-hostable option without a foreign parent company, provided the app's maturity and any relay operator are checked first.