The iPhone DevTeam just released first public iPhone OS 4.0b1 jailbreak. It is for iPhone 3G ONLY, Mac ONLY and devs ONLY. This release is not meant for average end-user, only for 3rd party app devs. Most of the apps are really really really buggy on OS 4.0 , and this way, devs can fix their apps before the OS is pushed by Apple. If you are still on FW 3.x DO NOT update to 4.0 just because now you got a tool to jailbreak it. Don’t say nobody warned you. If you still want to , you can find the tool and all the info ( READ CAREFULLY ) here…
HOW TO: Jailbreak iPhone OS 4.0 Beta 1 With RedSn0w [NOT Recommended]
