qutIM is free and open-source multiprotocol (ICQ, Jabber, Mail.Ru, IRC, VKontakte) instant messenger. Developed by Rustam Chakin & Ruslan Nigmatullin
License: Open Source
qutIM is a highly customizable instant messaging client that supports multiple protocols but lacks mobile support and voice calls. In contrast, Kadu offers voice and video calling capabilities, an active development community, and mobile access, but is less customizable and flexible.