You may tend to think of the AppleTV as a sort of walled garden, and you would mostly be right. Apple keeps tight control over what runs on their devices. That said, [David] decided to look closer at how the various ‘applications’ work. It turns out, the applications are nothing more than glorified web plugins. Using XML and Javascript, the apps simply define library function calls, giving them a consistent interface. So using fairly simply methods, the options really open up. Unfortunately, the method for adding new sites isn’t enabled by default.
Using a jailbroken AppleTV, [David] was able to do a fair bit of detective work and found a way to enable the ‘Add Site’ option, which allowed him to use his Raspberry Pi as a media server. The good news: you don’t need to jailbreak if you’re running 5.2 or 5.3… you should be able to recreate his success fairly easily. The bad news: things seem to have changed in 6.0. [David] isn’t sure if this was Apple intentionally closing a hole, or just not dotting all of their i’s.
[David] put all of his research up on Github, including the rough code. If you haven’t updated your AppleTV yet, and you have a Raspberry Pi to use as a media server, give it a try and let us know how it goes in the comments.

http://hackaday.com/2013/10/03/raspb...n-an-apple-tv/