Since Apple has renamed iPhone OS 4 to iOS 4, we thought we will update our jailbreaking guide for iOS 4.0 for both iPhone 3G and iPhone 3GS. The redsn0w 0.9.5b4 which was released for iPhone OS 4 Beta 4 (now iOS 4) will need an update to work with this version of iOS 4. But the instructions to jailbreak would remain the same. We will let you know as soon as an update is available.
UPDATE 1: The iPhone Dev Team has confirmed that the current version 0.9.5 of Redsn0w is can jailbreak iOS 4 GM on iPhone 3G. Download link here, and instructions are posted here.
For those who can legitimately activate to the iPhone3G 4.0GM seed, the “point to previous IPSW” redsn0w trick works and will jailbreak your 4.0GM. The “trick” is to point redsn0w at the 4.0beta4 IPSW instead of 4.0GM (do this after you’ve updated to 4.0GM and activated through the new iTunes 9.2 on your Mac). Since the carrier unlocks aren’t yet supported at 4.0, don’t do this if you use yellowsn0w/ultrasn0w/blacksn0w. Many JB apps are still pretty buggy in 4.0, so again this is mostly useful only for developers of those JB apps.
Note: If you’re experiencing MobileSafari crashes, double check that you’re running the version at the bottom of this page.
For those without legit iPhone3G 4.0GM seed access, please wait until the full public 4.0 release for updates to the jailbreak tools.
UPDATE 2: You can now jailbreak iPhone 3GS on iOS 4 GM using PwnageTool Bundles. More info can be found here, complete step by step guide can be found here.
UPDATE 3:Final version of iOS 4 has been released. You can jailbreak iPhone 3G (any baseband) and iPod touch 2G using Redsn0w 0.9.5b5-2. Download Redsn0w 0.9.5b5-2 for Windows and Mac, and then follow Step 1 to Step 7 posted here to jailbreak iPhone 3G and iPod touch 2G. You can unlock it (including 05.13.04 and 05.12.01 basebands) using Ultrasn0w 0.93 guide posted here.