Hey, sorry, was away from the boards for a while. The appleTV is jailbroken, not flashed with linux. There were a few hurdles w/r to some library dependencies but it was a (relatively) painless process.
I'm a little swamped with work right now, but as soon as I get some time I'll document the steps it took to get things running. I'm kicking myself for not taking better notes because I want to do the same things with my other appleTV =-(
I just stumbled on this post. Did you get anywhere with this? I had the exact same idea, if you can get CGMiner running on an appleTV it would be a perfect host box for a BFL ASIC. I'm working on getting it done right now, if you succeeded let me know if you have any pointers, thanks!