Limera1n Can Jailbreak the Apple TV
Erica Sadun has confirmed that she was able to jailbreak her Apple TV with Limera1n; however, it does not install OpenSSH at this time, so not much can be done with it.
The Limera1n page has updated to indicate that Apple TV jb is "technically supported". I can confirm that I put my ATV2 into DFU mode and was able to "jailbreak" it. But since no AFC services or OpenSSH were installed (let alone APT), there's nothing that really can be done with it at this time.
We'll let you know when the jailbreak is updated to install OpenSSH.