iOS 4 GM candidate was released for developers along with iTunes 9.2 beta. iOS 4 download is live and you can upgrade your iPhone 3GS 3G to iOS 4.0. If you were hesitating in upgrading your iPhone 3GS 3G to iOS 4.0 firmware because it would take away your jailbreak then your hesitations should be gone as iOS 4.0 is jailbreaked. Obviously, Hackers have also got their hand on iOS 4.0 GM candidate and just a rename can’t stop them from executing jailbreak on iOS 4.0.
A hacker known as msft.guy has managed to jailbreak iOS 4.0 {GM Candidate} on iPhone 3GS using PwnageTool. This means that he has been able to patch iOS 4.0 and cook a custom firmware which can be simply restored to iPhone 3GS. Surely, this mechanism to jailbreak iOS 4.0 does not upgrade the baseband and your previous unlock will be preserved on iOS 4.0 as well.
The PwnageTool bundle to jailbreak iOS 4.0 is not available yet. Lay users should stay away even if they get PwnageTool to jailbreak iOS 4.0. There is not much time left in the stable releases of tools like PwnageTool 3.1.6 and redsn0w 0.9.5 by iPhone Dev Team and sn0wbreeze 1.6 by ih8sn0w. We also hope that limera1n jailbreak for iOS 4.0 will be also available.
A working demonstration of iOS 4.0 jailbreak can be seen in the video
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Update: Don’t worry about iPhone 3G. redsn0w 0.9.5 can Jailbreak iOS 4.0 iPhone 3G.
