As is usually the case with these open source reimplementations, the game assets (textures, sounds) must still be retrieved from the official installation / ISO.
And there seems to be some market for nostalgia around selling old games. We can see new versions of old consoles, bundles of old games (with preconfigured emulators), ...
https://www.copyright.gov/help/faq/faq-duration.htm
So we are solidly inside the copyright window.
Sounds reasonable.