Holycrap that is AWESOME! That just gave me all kinds of ideas. They need to start making those parts out of carbon fiber instead of milled billet...and then figure out a way to make them snap together rather than secured by screws.
I just did a little more research on that DVD and found a link to it on Amazon as well - but they show it as "discontinued by source". The DIYguns site might be the only current vendor with 'em - have to look around some more.
As for materials, yeah, I could see a number of possibilities, maybe with a metal "drop-in" trigger pack, a~la H&K or the new Sig P250 handgun. It gets interesting with regard to the older rules for "80%" receivers, too. You could probably contract out some of the pieces without fear of those companies getting popped for unlicensed manufacture. Yeah, *lots* of ideas.
As for the fasteners, I don't mind the use of screws. The AK guys would probably insist on rivets, though. ;-) A "snap-together" AR sure would be cool, though. The rifle was mocked as a toy for years - now it could actually be assembled like one.