Well I believe it was Eugene Stoner who came up with the AR-10, but Armalite actually started building them, which then got bought by Colt, who licenses to FN and Bushmaster, I think...not sure, but the prod rights to the weapon have certainly changed hands quite a bit.
I'll try and dig that info up.
*EDIT*
K, here we go...
Stoner worked for Armalite and designed the AR-10. 1957, the Army asks Armalite for a 5.56mm auto rifle and thus is born the AR-15. 1960, Stoner leaves Armalite and joins Colt - Armalite doesn't like the way development is going and sell the design to Colt around the same time.
1988, the US division of FN becomes the primary DoD contractor for the M16.
Now, Armalite apparantly still builds them, as well as FN, Bushmaster, Diemaco (under license) and a bunch of others, but Colt is the one who sold the designs to them.
So from 1960 on, the whole M16 family is primarily the property of Colt, but Colt only makes them now for civil and law-enforcement markets.