@P0sixninja of the Chronic Dev Team announced that the latest version of Greenpois0n (RC5) is now available for download. However, the first release is only for Mac users and is still on the Beta stage. Windows users may need to wait a little more time while the Dev Team is still working on it.
Greenpois0n RC5 can jailbreak iPhone 4, iPhone 3GS, iPhone 3G, iPod Touch 4G, iPod Touch 3G, and the iPad – on iOS 4.2.1 untethered. Unlike the iPhone Dev Team’s Redsn0w 0.9.7 jailbreak, the Greenpois0n jailbreak won’t need the iOS 4.2 Beta 3 SHSH blobs along the process. P0sixninja also reiterated that Greenpois0n RC5 doesn’t support hactivation, which means you have to hactivate your device through iTunes. He also added that the latest version of Greenpois0n has already been patched on iOS 4.3.
Please note that Greenpois0n needs your iPhone to have iOS 4.2.1 installed and for iPhone 3G and 3GS users, your baseband will be updated to 5.15.04. If you need baseband 5.15.04 unlocked, I strongly suggest to stay away from upgrading to iOS 4.2.1. The iPhone Dev Team has a tricky way of upgrading baseband 5.15.04 to iPad baseband 6.15.00 and finally unlocking it; however it uses the Redsn0w tool and there’s no way the Chronic Dev Team’s Greenpois0n can do that, just yet.
Greenpois0n RC5 for Mac can be downloaded from this link (original site); however it may still continue encountering too much server loads for the time being. Thanks there’s a mirror download link as an alternative.
Update: Greenpois0n RC5 for Windows is also available for download.