BLENGOK

ChitChat was an open source instant messaging client for Mac OS X supporting the Yahoo! Messenger protocol. It enabled users to chat with each other over the global Yahoo! chat system. The last version, ChitChat 1.2, had a more refined user interface, speed improvements, Address Book support, IM reformatting, an improved events system, and numerous bug fixes. ChitChat was programmed in the REALBasic programming environment.
You can also login with your facebook username and password and can chat with your facebook friends.