iPhone OS 4.0 “Beta” has just been released yesterday and today @MuscleNerd from the iPhone Dev Team already uploaded a movie on YouTube showing a jailbroken OS 4.0. Its probably done with Spirit which is an userland-jailbreak and will work on all OS versions. The userland-jailbreak is an untethered jailbreak. » iPhone OS 4.0 Already Jailbroken [jailbreak]