Fully open source instant messaging server and clients. No proprietary components or non-free dependencies. Backend in pure Go (GPL 3.0), with a command-line administration tool in python + gRPC. Clients for Android, iPhone, and Web - ReactJS (all licensed under Apache 2.0). Persistent storage MySQL and RethinkDB. Tinode is not XMPP/Jabber. It is not compatible with XMPP. It's meant as a replacement for XMPP. On the surface it's a lot like open source WhatsApp or Telegram.