For reasons best known only to them, Apple renamed their iPhone OS to iOS, specifically their upcoming iOS 4.0 and hence we wanted to let you all know about the same, but at the same time we must make it clear that except for the name change, everything else remains same including the jailbreaking mechanisms.
Jailbreak iOS 4.0 on iPhone 3G/3GS/4 and iPod Touch with redsn0w 0.9.5
Redsn0w 0.9.5 Beta is the tool to jailbreak iOS 4.0 on iPhone 3G & iPhone 3GS. It is just a matter of time that iPhone Dev team will update their beta tool to jailbreak iOS 4.0 GM Candidate released today to developers. So all our guides to jailbreak iPhone 3G 4.0 & iPhone 3GS 4.0 will still hold true.
iOS 4.0 will be made available to everyone via the iTunes update on June 21st 2010. If you are looking forward to jailbreak or unlock your iDevice, you better not upgrade your firmware to iOS 4.0 until the jailbreaking and unlocking tools are available.
Meantime, if you are on iPhone OS 3.1.3, you can follow our step-by-step guide to jailbreak iPhone 3GS with Spirit here and iPod Touch 3G untethered here. You can also use redsn0w 0.9.3, redsn0w 0.9.4 or sn0wbreeze.
Update: Guide to Jailbreak iOS 4.0 GM candidate is here. make sure you read the warning within the post before proceeding.