RetroShare (Decentralized chat, email, forums, and file sharing)

RetroShare is a Open Source cross-platform, Friend-2-Friend and secure
decentralised communication platform. It lets you to securely chat
and share files with your friends, family and coworkers, using a
web-of-trust to authenticate peers and OpenSSL to encrypt all
communication. RetroShare provides filesharing, chat, messages,
forums and channels.

To build the "Tor Only" version, use the build option "RETROTOR=yes", e.g.

  RETROTOR=yes ./retroshare.SlackBuild