Did Clarke write the sequel novels after the movie, I wonder? I can see movie-making folks getting on board with it if the first one experienced a lot of success at the time, and then if you have Clarke saying he'll write more, there's usually someone with money wanting to perpetuate something successful in the hopes of generating more money off it. At least, that's my impression, given how many sequels some other movies got. *cough* Planet of the Apes *cough*
I'm ashamed to say I've never actually read anything by Clarke or Asimov. My education in science fiction is mostly television and movie-based.