Apple's copyright infringement claim starts with the observation that jailbroken iPhones depend on modified versions of Apple's bootloader and operating system software. True enough -- we said as much in our technical white paper describing the jailbreak process. But the courts have long recognized that copying software while reverse engineering is a fair use when done for purposes of fostering interoperability with independently created software, a body of law that Apple conveniently fails to mention.
So, Steve Jobs can say what he wants. The courts are the final arbiter. Jailbreaking, like "rooting" an Android phone, perfectly legal. Warranty voiding, maybe, but legal.
