Again, according to an article written by yahoo on May 25, 2007, they are in the process of working on the Mac Version.
See Below for part of that article and link. Mac chat rooms: We are already beta testing a new version of Messenger for Mac that includes, among its many improvements, native support for chat rooms. Yes you read it correctly, native support for Mac chat rooms! Client software is tricky, of course, and sometimes the "bug fixing" takes longer than we anticipate. But we believe it is more important to have a delay and get it right, than to rush and make a mistake. Like the chat rooms team, the Mac team is a small one, but they make up for it with their talents. As a Mac user myself, I am very glad that we continue to actively support such a great platform as the Mac OS. We appreciate your patience while we get this next version ready. http://blog.messenger.yahoo.com/blog/2007/05/25/chat-rooms-state-of-the-union/
