Matrix is an open protocol for real-time communication. It is designed to allow users with accounts at one communications service provider to communicate with users of a different service provider via online chat, Voice over IP, and Videotelephony. Developed by Matrix.org
License: Open Source
Gajim is a lightweight, XMPP-focused messaging client that excels in private messaging and customization, while Matrix.org offers a robust communication platform with end-to-end encryption and extensive group features. Matrix.org is more suited for users needing secure, versatile communication across different platforms, especially for larger groups.