KVIrc is a graphical IRC client for Linux, Unix, Mac OS and Windows. Developed by HelLViS69 - code - hellvis69 @ netsons.org
License: Open Source
Chatzilla is a lightweight IRC client that operates as a Firefox extension, making it easy for beginners but limited in functionality and browser compatibility. KVIrc, on the other hand, is a standalone IRC client that offers advanced features and customization options, making it suitable for more experienced users.