Ring4 Meeting - Dead simple video conferencing - free, in browser
Prosody - Prosody is a modern flexible communications server for Jabber/XMPP written in Lua.
Fellow.app - A manager’s co-pilot for 1:1s, meetings, feedback & goals 🚀
Openfire - Openfire (formerly Wildfire) is a cross-platform instant messaging (IM) and groupchat server.
Everleagues - Everleagues is a cloud-based application that offers team communication, file sharing and storage, data tracking, and activities management.
ejabberd SaaS - Realtime XMPP and MQTT Software and Infrastructure as a Service.