Hummers are nothing more than converted Chevy Tahoe's for the H2 and Colorados/Canyons for the H3. I don't know which chasis they use for the big one. Chevy trucks with some window dressing is all they are, just like the Chevy-GMC relationship. Same truck, different body parts.
The original HUMVEEs were designed and made by AM General in Indiana, so I think the design is original and not a GM/Ford/Chrysler knock-off. BTW, I did not know about the use of the GM bases for the H2 and 3 tho. Interesting.
And Haz, no problem with the chips - I expect something like that since I think the Chinese are at war with us, following Sun tzu's precepts, and not Western ideas of warfare. It would be fairly easy, though, to reverse engineer the computer code to determine exactly what the computers are telling the vehicle to do, although it may take a while. Fifteen years ago there were over 500k of computer instructions in automobile controllers. With memory cheap, and the need to exert more control to meet fed guidelines, it is probably a whole lot more now.
No need to implant Trojan horses tho - one EMP pulse will do most of them in.