- [jackal](https://github.com/ortuman/jackal) - XMPP server with focus on stability, simple configuration and low resource consumption. `Apache-2.0``Go`
- [Kontalk](https://www.kontalk.org) - Kontalk is an Open Source Messenger, similar to WhatsApp (app for android only currently), including end-to-end encryption, server is based on Tigase XMPP Server. ([Source Code](https://github.com/kontalk/androidclient)) `GPL-3.0``Java`
- [Metronome IM](https://metronome.im/) - Fork of Prosody IM. ([Source Code](https://github.com/maranda/metronome)) `MIT``Lua`
- [MongooseIM](https://www.erlang-solutions.com/products/mongooseim.html) - Mobile messaging platform with a focus on performance and scalability. ([Source Code](https://github.com/esl/MongooseIM)) `GPL-2.0``Erlang`
- [Openfire](https://www.igniterealtime.org/projects/openfire/) - Real time collaboration (RTC) server. ([Source Code](https://github.com/igniterealtime/Openfire)) `Apache-2.0``Java`