RetroShare is open source software for encrypted filesharing, serverless email, instant messaging, online chat, and BBS, based on a friend-to-friend network built on GNU Privacy Guard (GPG). Developed by DrBob
License: Open Source
Signal is a user-friendly messaging app focused on privacy with strong encryption and a straightforward setup, while RetroShare is a decentralized, community-oriented platform that emphasizes secure file sharing and private networks, but may require more technical knowledge to use effectively.