Openfire - Openfire (formerly Wildfire) is a cross-platform instant messaging (IM) and groupchat server.
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
Prosody - Prosody is a modern flexible communications server for Jabber/XMPP written in Lua.
Supabase - An open source Firebase alternative
Matrix.org - Matrix is an open standard for decentralized persistent communication over IP.
Etebase - Etebase makes it easy to build end-to-end encrypted applications by taking care of the encryption and its related challenges.