add retroshare, closes #236

README.md

@@ -228,6 +228,7 @@ Some [Groupware](#groupware) solutions also feature calendar/address book editin
   * [Let's Chat](https://sdelements.github.io/lets-chat/) - A persistent messaging application that runs on Node.js and MongoDB. `MIT` `Nodejs`
   * [Mumble](http://wiki.mumble.info/wiki/Main_Page) - low-latency, high quality voice/text chat software `BSD` `C++`
   * [Node-Chat](https://github.com/IgorAntun/node-chat) - A not-so-basic open-source chat with admin features. - `MIT` `Nodejs`
+  * [RetroShare](http://retroshare.org) - Secured and decentralized communication system. Offers decentralized chat, forums, messaging, file transfer. ([Source code](https://github.com/RetroShare/RetroShare)) `GPLv2` `С++` 
   * [Rocket.Chat](http://rocket.chat/) – Teamchat solution similar to Gitter.im or Slack - `MIT`
   * [Synapse](https://matrix.org/blog/project/synapse/) - A server for [Matrix](https://matrix.org/), an open standard for decentralized persistent communication ([Source code](https://github.com/matrix-org/synapse)) `Apache` `Python`
     * [Matrix Console Web](https://matrix.org/blog/project/matrix-console-web/) - A web client meant to be a showcase of Matrix capabilities, and reference implementation of the Matrix standard ([Source code](https://github.com/matrix-org/matrix-angular-sdk)) `Apache` `Javascript`