Converse.JS - A free and open-source chat client for your website
Cachet - Cachet is a free, open source status page for your API, service or company. Built with all of the features that you'd expect from a status page.
Rocket.Chat - Rocket.Chat is a Web Chat Server, developed in JavaScript, using the Meteor fullstack framework.
cState - 🔥 Free & open source under MIT!
Lets Chat - Open source self-hosted chat app for small teams
Status.io - Status.io is a platform for system status pages and status notifications. Companies rely on Status.io to track outages, schedule planned maintenances, broadcast status notifications, and much more; and their customers love the transparency.