Most emulation projects are completely legal and something to be proud of. And it’s some of the technically most challenging problem solving that coders could have on their resume. Making a good emulator is incredibly impressive. You very much can get a job based on that.
Edit: Ah apparently there is a bug with the seamless UI switching. To play it with mouse and keyboard UI on steamdeck, you have to go full mouse and keyboard. Map all your buttons to the keyboard keys that would perform the same action. There are community button configs for that though. The good news is that it is likely a bug, seamless switching is supposed to work, and hopefully will at some point.
Original less-informed message: Steam deck can also use the mouse and keyboard UI. And PC can use the gamepad UI. That seems to be the difference you are talking about. It auto switches interface based on what you touched last, so you just need to setup mouse controls on your steam deck, lots of options for how you want to do that. Touchscreen, trackpad, a key combination to activate mouse mode on one track pad and another combination or the same one to turn it back off, plugging a physical mouse in… I’m sure there is more, but either way, one of those should get you the mouse and keyboard UI on steam deck.
The only thing they did wrong was having the key dumping info associated with them. Nothing else needed to have been done different. Without that, they would have been completely legal. Dumping roms is totally fine.
You want people to know it was you that did all this technically impressive work and problem solving. Had they not done that one thing, they would have been fine putting their names on their work.