iPhone Dev-Team had earlier made news when it had released a redsnOw jailbreak for iPhone 3G and 3GS. The team is now looking for
testers for its "backup plan" for 4.2.1 untethered jailbreak. The test has been restricted to Mac platform and it requires testers to have 4.2b3 IPSW on their Mac. The testers will apparently help Dev-Team in finding the bugs in the program before its general release.
Dev-Team's earlier jailbreak allowed carrier unlocking but it was limited to iPhone 3G and 3GS. It also had certain shortcomings. The most palpable one was its inability to go back to normal condition. This meant that once you use this tool to jailbreak your iPhone, you effectively void the warranty on your phone as it can be proved that the phone has been tempered with.
So, in case, you are willing to lend your help to the Dev-Team and you fulfill all their conditions, then you can follow @redsn0w_tester on twitter for further information.
Source: Dev-Team Blog, Image: Apple