FireCore has just released Seas0nPass 0.7.7 that features support for Lion and a handful of bug fixes. It’s generally designed to jailbreak your atv2 running iOS 4.3.x (Apple TV 2 4.2.2 software version) but, according to nitoTV, it also supports the latest iOS 5 beta.
Similar to PwnageTool, Seas0nPass allows you to jailbreak your atv2 by creating custom Apple TV IPSW files and restoring them in iTunes. The new version of Seas0nPass is Mac only – it adds support for Lion and fixes Mac specific bugs.
Here is the tutorial on how to jailbreak your Apple TV 2 on iOS 4.3 (Apple TV 4.2.2) or iOS 5 using Seas0nPass 0.7.7: