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
Kopete is primarily focused on instant messaging with a user-friendly interface and support for multiple chat protocols, while Jitsi excels in video conferencing with high-quality audio and video, making it ideal for larger group calls. The choice between them depends on whether the user prioritizes messaging or video communication.