Nice find. But that one comment about THX being too similar to Logan's Run, which didn't come out until five years later? (Unless they refer to the novel?) My head hurts. ;)
There's a stutter or glitch at the point THX is standing up on the youtube clip and erri_wan's version. Both could be from the same broadcast?
I've been thinking I should ask the seller of that 16mm print if they're going to re-list the auction anytime soon. I didn't want to ask too many questions about it for fear the price would go up again. Pretty sure the asking price went up after I inquired about the Warner logo.
There's also an old betamax tape of THX I'm curious about.
http://cgi.ebay.com/Rare-THX-1138-BETAMAX-Tape-George-Lucas-/370455404600?pt=US_Movies_Other_Formats&hash=item5640dce038
Alas, my old Sony beta doesn't work so good these days.