"“We were blown away when we saw the results, in disbelief that AI could recreate the iconic PAC-MAN experience without a game engine,” said Koichiro Tsutsumi from BANDAI NAMCO Research Inc., the research development company of the game’s publisher BANDAI NAMCO Entertainment Inc., which provided the PAC-MAN data to train GameGAN. “This research presents exciting possibilities to help game developers accelerate the creative process of developing new level layouts, characters and even games.”"

Emphasis mine.

Also, while I disagree that this would be real "fair use" (rather than Internet Pundit fair use, which is virtually indistinguishable from "I want this, so it must be legal") without permission, it wouldn't matter anyhow. If nVidia did this without permission and tried to distribute exactly what we saw, it would also be a trademark violation. Pacman is almost certainly in the top 1% of defended trademarks, if not .1% or .01%... not a great thing to try to use without permission.

I'm not convinced the visuals would be fair use. However it was certainly done in partnership with Namco. It's celebrating Pac-Man's 40th anniversary and says at the bottom of the article: PAC-MAN™ & ©BANDAI NAMCO Entertainment Inc.

Plus there is a massive give away that Namco approved this within the article:

We were blown away when we saw the results, in disbelief that AI could recreate the iconic PAC-MAN experience without a game engine,” said Koichiro Tsutsumi from BANDAI NAMCO Research Inc., the research development company of the game’s publisher BANDAI NAMCO Entertainment Inc., which provided the PAC-MAN data to train GameGAN. “This research presents exciting possibilities to help game developers accelerate the creative process of developing new level layouts, characters and even games.”