I mean, yes that's how progress works. Has OpenAI got a patent? If not it's fair game.

We don't make people figure out how to domesticate a cow every time they want a hamburger. Or test hundreds of thousands of filaments before they can have a lightbulb. Inventions, once invented, exist as giants to stand upon. The inventor can either choose to disclose the invention and earn a patent for exclusive rights, or they can try to keep it a secret and hope nobody reverse engineers it.