Actually, I doubt that they are full auto. I have no doubt that they have at least three safety settings... Safe, single, 3 shot burst. IIRC, most M-16A2s issued by the US military no longer offer full auto, as it can be a huge waste of ammo.
But as to the question "is that a semi-auto, civilian version of the M-16?" The answer is NO!
Semi automatic is individual counselling.
Full automatic is group therapy.
There is actually a M-16A3... I got to see it about 4 years ago during plebe summer, since every year the use brand new weapons. I cant remember if it had 3 burst or auto though.