Details on how Joost can be launched on AppleTV can be found in awkwardtv.org wiki. Joost seems to behave normally under AppleTV once it is set up. However setting up and configuring channels is not easy and it is recommended that you do your channel configuration on an a mac before transferring the files to ATV. Joost has fairly good support for the Apple remote but does not have the capability to exit using the remote. However it is fairly easy to crash Joost and that exit that way. All testing for this How-To was done on an Intel mac and Joost for Friends 0.10.3
Find out how to do it by reading the full Wiki post.
The Apple TV is a set top box manufactured, marketed and sold by Apple. It is a network device designed to play digital content originating from any Mac OS X or Windows computer running iTunes onto an enhanced-definition or high-definition widescreen television. Apple TV can function as either a home theater-connected iPod device or a digital media receiver, depending on the needs of the user.
Thank you Brian Moura for the tip!