Either a fake or big misunderstanding.
Generating the fake boarding pass is the easy part.
Try it your self:
?http
/www.ipassme.com/demo/boardingpass/pass/
Good luck with passing any check at the airport!
And, of course, please don't try!
The "string" in the barcode is pretty easy to hack. It's not different from the one used "until yesterday" on the printed boarding pass. Just a short collection of info such as name, flight number, confirmation code, seat, etc.
I'm pretty sure at the gate they verify the info with their DB's. I'm refusing to think otherwise. Besides, Apple is pretty clear about that: "it's a retailer responsibility to verify the data in the pass".