Why would they ask Google for permission?

Because youtube is owned by google and google can stop download at scale

Can google stop them? It’s trivial to download YouTube videos

It’s trivial to download some YouTube videos.

But I am quite sure that if you start doing it at scale, google will notice.

You could be sneaky, but people in this business talk (since they know another good paying job is just around the corner) so It would likely come out.

OpenAI can afford to build a scraping network, built with thousands of proxies.

They can afford to. But will Microsoft risk doing that and massive possible lawsuit from Google.

Google is also owns a lot of it's own backbone, so It would be a lot easier for them to play network games.

And they could even try to be sneaky and try poisoning the data if it comes to that.

And since OpenAI konw that, since they probably have people that used to work at google at some point, they are unlikely to try.

Even less likely if Microsoft would know. MS is probably the only company that has even more layers than Oracle and they would not approve.

One way would be to get people to let AI watch as they interact with computer (watch YouTube or perform other tasks). You might even be able to outsource some of the computing to the local system.