Does Marc Okrand have creative control over Klingon?

[Macnerd]

I know that James Doohan created some words for the Klingon characters in the original Star Trek.

Can anyone make changes to Klingon(add words, change grammar, create an alphabet) or is Marc Okrand the only one?

Some websites state that conlangs can't be copyrighted because they aren't intellectual property like a novel or music.

I'd love to create a conlang. I have ideas for grammar & words & syntax that I've put on paper but I doubt that I could copyright thoughts.