Greenpois0n to Jailbreak iOS 4.2.1 on iPhone, iPod Touch, and iPad has been out since some days. It was first released for MAC and then a Windows version came out. Greenpois0n RC5 B4 is the latest release which also supports to jailbreak Verizon iPhone 4 on 4.2.6 firmware.
Greenpois0n for Apple TV 4.2.1 is being worked on and will be released as Greenpois0n RC6. It will be more polished and this Greenpois0n 4.2.1 is expected to be available for Windows and Mac at the same time. We also expect that Greenpois0n 4.2.1 will also be available for Linux this time.
On a side note, do you think Grenpois0n 4.3 will be available for iOS 4.3 Jailbreak once iOS 4.3 is out while Redsn0w 0.9.8 is also being worked on?

