It will be open source, end to end encrypted using Signal’s double ratchet encryption protocol, and he plans to make it easy for fediverse platforms to integrate it. The beta will release later this month.
He’s also the creator of https://fedidb.org btw
All existing messengers have “no walls” if you consider they all transfer data via TCP/IP. Except the wall is the encryption/higher level protocol. Now just replace TCP/IP with federated servers. Different messengers will be unable to communicate with each other because they’d need to implement the same encryption.
If you’re able to standardize the encryption then things can interoperate if it’s fediverse based or not.