The Apple iPad has been jailbroken according to notorious hacker, MuscleNerd, who published this video showing the achievement. A member of the infamous iPhone Dev Team, the developer took just one day to crack Apple security, which he managed through use of a variant of the existing iPhone OS 3.1.3 jailbreak. Most jailbreaks use vulnerabilities either in Safari or the OS itself to grant unrestricted access, this is thought to have been the M.O. for this break-in. What’s it mean? For most of us, not too much, but if you want to install software other than that available from the App Store then…