Hudsong
I have Mobipocket on a pda with OSX on my laptop. The Mobipocket PDA software told me what the PID of the device was - I then went to their website and registered it. It took as long as it takes to fill in the form to set up an account. It would be exzpect that Mobipocket on the CyBook would work in the same way. But if you're concerned why don't you contact Bookeen direct at :
contact@bookeen.com