The "tower" is just a Mac mobo/ps/guts stuck in a PC clone tower. The pizza box is going to be custom manufactured, and won't be available for a couple of weeks at the earliest.
You could assemble your own Mac clone tower now if you wanted. You can get the mobos from eBay, or MacResQ, along with the power supply. Get yourself a case, add your CPU (available from Macsales.com and elsewhere), your HD, your optical drive, kb/mouse, power up and install your OS. It's not rocket science, just hobbyist electronics.
The benefit of going with Happyware is that the price will be a little cheaper, since he's buying his parts in bulk and reselling them. Also, getting a Mac mobo to sit correctly in a PC case is a bit of a challenge, since the screw positions and holes on the mobo/case aren't compatible. Not sure how he's getting around this.
One of the guys from TechTV created a similiar Mac clone and had the same problem. He got around it by using plastic twist ties to mount the mobo to the case. Not pretty, but it worked...