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
IM+ is a versatile messaging app with support for multiple platforms, while Jitsi is a robust video conferencing tool focused on security and open-source accessibility. IM+ is better suited for multi-messaging needs, whereas Jitsi excels in providing high-quality video calls.