Orc can not be copyrighted as it refers to a mythical creature passed down the ages.
ORK can be copyrighted as it takes the mythical creature, puts it in space and gives it a specific difference (being plant based in it's physical makeup and pyshicly being able to make guns and shit work that should not)
Disney does that a lot. You can't Copyright just say, the Little Mermaid. So it's "Disney's The little mermaid" taking the public domain story and only protecting their version of it. As well as characters. Yeah I got a 6yrd daughter and they describe them "The beautiful Belle" The enchanting Ariel or the Syphilus Shawna for legal rights to that character.
So Orc is everything Orc outside of 40k. And Ork is the 40k or Fantasy and GW creation...