Mattermost is a secure, open source platform for communication, collaboration, and workflow orchestration across tools and teams.
Glip is instant messaging for teams and businesses to communicate and get work done at the same time. In Glip you work where your conversations are, so you always know what your team is doing and what needs to get done next.
AllAnswered provides an all-in-one knowledge management system including an advanced Wiki and Questions & Answers (Q&As) with built-in workflow and knowledge life-cycle management to keep your knowledge base up-to-date.
Self-hosted chat for small teams.
As stated at https://github.com/sdelements/lets-chat/issues/781 , the project is no longer developed since August 2017. Last version, 0.4.0, released in June 2015, can be still downloaded from GitHub together with the source code.
Simple yet powerful open source slack alternative chat platform for teams and organizational communication. Keep your conversations in your control, free from data mining and ads. Safe from prying eyes and secured with encryption.
Fuse Chat is a Video Chat script userfriendly php socket.io script With is fully responsive design whatever if you are using a mobile a computer or even a tablet will always fit your screen and give you the best chat experience possible.
Private and Secure Instant Messenger for Office designed specifically for keeping remote employees and multiple offices in sync.
"Give your team the freedom to chat, talk, share and interact together from anywhere, on any devices" by using it.