Well both in the movie although cryptic and hidden, and in the script and novel David just tried recreating the xenomorph from the info he got from the space engineers, and now I cant remember if he even found an egg he based a lot of his research on. Which explains why his xeno grew up faster and skipped the chestburster stage, and also why its way more stupid and more aggressive than the xeno we see in the original movies. Attacking the crane by jumping at it.......
And also remember in prometheus they had on the murals the xeno shown, and also the derelight ship has long time ago crashed on lv-426 at this time unless Ridley rewrite that part in the next movie, which would go against what Giger and Dan O banon and others confirmed when making alien and the space jockey is fossilised, dont get me started on you cans ee teeth and its tounge and eye etc and not a suit.
So to me David isnt the creator, just trying to recreate the creature and make it better and use it for his own gains and experiments. Those proto morphs and deacon etc I gladly let him take credit for however.