Orc's is fine. Chapterhouse was a testcase really. They picked the company that took the 'p' more than others and went to town.
Orc is a long established name, so couldn't be protected. It wasn't original to GW. As a result of the other terms like Space Marine etc in that case being deemed too common to be protected they renamed pretty much their entire range of paints and the vast majority of the miniatures that had common names.
Orcs became Orruks with the introduction of AoS.
Orks I'm not sure about to be honest. But considering it is just a letter swap from Orcs I doubt it would be either.