Jitsi (formerly SIP Communicator) is a free and open source multiplatform voice (VoIP), videoconferencing and instant messaging application. Developed by University of Strasbourg (France), plus many others.
License: Open Source
Psi is a versatile XMPP client with strong encryption and protocol support, making it ideal for users who prioritize privacy and customization. Jitsi, on the other hand, excels in ease of use and seamless video conferencing without the need for accounts, making it suitable for quick meetings and collaboration.