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
RetroShare offers a decentralized platform emphasizing secure messaging and file sharing, making it suitable for users valuing privacy. In contrast, Calypso focuses on simplicity and integrated task management, appealing to users looking for an easy-to-use tool for collaboration.