Jitsi can Installated on MAC
Download MAC OS X packages and download (No-JRE Packages) Mac OS X 10.6/10.7 from following link:
OS X Support for tel: and callto: URIs
Jitsi is a free messenger client for Mac, which supports most major protocols and even supports video and audio conversations. Simply choose the IM protocol that you'd like to connect to including SIP, Google Talk, XMPP/Jabber, MSN or Windows Live Messenger, AIM, Bonjour, ICQ, Yahoo Messenger and Facebook chat.