Psi is a free instant messaging application designed for the XMPP network (including Google Talk). Fast and lightweight, Psi is fully open-source and compatible with Windows, Linux, and Mac OS X.
License: Open Source
Xabber is an open-source, lightweight client focused on XMPP, making it ideal for users who prioritize customization and speed. In contrast, Psi offers broader platform support and stronger security features, appealing more to users who need a robust and user-friendly interface.