According to West End Games, here is what they say about the license:
"John was hired before West End Games completed the StarGate deal, which was in the works before the Chapter 11 bankruptcy. When Humanoids bought West End Games, it decided to go with the DC Comics license. The StarGate deal was dropped.
Thus, while MGM did try to license the property, they were never able to - at least not to West End Games. I am surprised that no other company has attempted to pursue it; it must be quite expensive now."
I also note that the Gurps game referenced above is "fanfiction" and done without permission of the copyright owner. Pretty gutsy thing to do, actually.