I guess it comes down to the minutiae of what's in Glen's agreement -- does "film rights" encompass everything used in the whole, original series, or only the elements that Larson created in the Pilot Episode (Michael, Devon, K.I.T.T., Wilton, etc.)?
Glen owns the rights to everything that was used in Knight Rider the TV series including all
characters, concepts, creations, etc. as part of his deal to have
creative control over everything invented in the Knight Rider universe.
It makes no difference that Steven E. de Souza wrote the script because by doing so and getting paid for it, it became
property of Universal and since Glen was
executive producer actively involved in what was being done, Glen's property as well.
I don't know how payment terms go because I don't know what was in Steven's contract but I would assume since Glen had a clause that predates Steven's involvement, Glen wouldn't have to pay him.
This means however that both Universal and Glen can use the characters invented in their respective properties. So it's possible to have two different characters named "KARR" or "KITT" or "Goliath" with entirely different looks or characteristics.
Hypothetically speaking you could make
Goliath an aircraft carrier in one show and a government satallite in the movie, it doesn't matter.
KARR was based on KITT. KITT was Larson's creation. KARR is a derivitive work of KITT, so to speak. (in real life KITT came first, not KARR).
FuzzieDice is correct, K.A.R.R. was inspired as K.I.T.T.'s opposite, Steven E. de Souza used Glen's characters and concepts to create K.A.R.R. therefore neither one can argue who invented what first because they're both borrowing from one another's concepts.
It's like when someone writes a
Star Wars book for Lucasfilms and invents new characters (Mara Jade, Thrawn, The Vong), no matter what circumstances of invention or design those characters then become property of Lucasfilms and in that manner Lucas's property
even if he didn't invent them.
You could argue that Lucas had an "idea" of what Boba Fett would be, but he didn't actually build the backstory himself nor the design work (at the time, not counting the prequels here), he hired other people to do it for him (see link below) and yet he still owns the rights to everything associated with said character.
http://www.bobafett.com/manual/btm/artists/index.shtml
Since the Knight Rider movie is not a continuation of the original TV series but still
Glen's world, any characters such as
Goliath, K.A.R.R., Garth, can be recreated or reintroduced any way that Glen feels he wishes to do so.
=VK=