The following was just posted on the Joost blog:

"

Mac Intel users, rejoice! Joost for Mac Intel is now available in beta version. We hope you enjoy it as much as we enjoyed making it. With the help of a handful of great people, we were able to leverage both the tremendous work done by the Client team for the Windows version as well as the cross-platform power of Mozilla. As a result, we have a Mac version that looks very much like Joost for Windows, while behaving very much like a Mac application.

Many thanks to our courageous alpha-testers who provided useful feedback and helped us squash the last few serious bugs. Still, let me remind you: it’s a beta. There are a few bugs left (read the release notes). And please report any new bugs you find. We’ll send t-shirts to the submitters of the best bug reports!

"

I am still looking for an invite.  Send one my way if you have one.  I would love to beta test the mac client: bmaltais@gmail.com