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 versatile, open-source platform that excels in video conferencing and security, making it suitable for professional and collaborative environments. In contrast, Windows Live Messenger, now discontinued, offered basic messaging and audio chat features, but lacks modern functionalities and support.