iPhone OS 4.0 Beta Jailbroken

Well, that didn't take very long. Less than a day after the iPhone OS 4.0 beta was released to developers, iPhone hacker Musclenerd has already jailbroken it.
So as not to jeopardize a working jailbreak technique before the final iPhone 4.0 update hits handhelds, no one's talking about the exact jailbreaking method being employed here. [...:]