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 an open-source video conferencing tool that excels in security and customization but lacks many collaborative features, making it less suitable for corporate environments. Spark, on the other hand, is a comprehensive collaboration platform that includes chat, file sharing, and user management, making it ideal for business use but potentially overwhelming for personal users.