Obviously, everything written on that blackboard, from (and including) "The key for the SYSTEM DISK is:" and to (and including) www.ziPhone.org is NOT something that was written on that board by Einstein, but was superimposed there. The stuff in the middle is some sort of hex address code (I have NO idea what it is), but apparently, the "Until then, enjoy the KEY" comment is some sort of humorous reference to all that. Seems it's some sort of "inside" joke or something of that nature. Or maybe "the KEY" is a reference to ZiPhone jailbreak itself.
It's an encryption key that, according to Zibri, is so embedded in the OS that it isn't likely to be changed--in fact Zibri actually called it hard-coded. This key was originally thought to be the key used by third-party (SDK) applications.
But instead it appears to me like the "key to the kingdom," if you will, of the iPhone. This key is what, apparently, allowed Zibri to be able downgrade the bootloader, which in the past was only something Apple could do (but likely wouldn't, as it's a risky endeavor).