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
Jitsi is a robust platform primarily focused on video conferencing, providing ease of access and high participant limits without the need for accounts. In contrast, Psi+ is a flexible instant messaging client that supports various protocols but lacks the advanced features found in dedicated video conferencing solutions.