Rocket.Chat
46kCommunications platform that puts data protection first (alternative to Gitter.im and Slack).
Communication - Custom Communication SystemsMIT
All-in-one customer engagement platform from lead-gen to post-sales, from WhatsApp to your website. With omni-channel live agents and AI-powered chatbots (alternative to Intercom, Zendesk, Tawk.to and Tidio).
Communications platform that puts data protection first (alternative to Gitter.im and Slack).
Notification infrastructure for developers.
Platform for secure collaboration across the entire software development lifecycle, can be integrated with Gitlab (alternative to Slack).
Customer communication platform (alternative to Intercom and Zendesk).
Push notifications to phone or desktop using HTTP PUT/POST, with Android app, CLI and web app, similar to Pushover and Gotify.
Zulip is a powerful, open source group chat application.