Perhaps I'm mistaken but the project doesn't need a copy of the original ROM at all right?

To be clear; I don't really understand the law around this - my own country is based on case law which means that even if I wanted to open source some of my reverse engineered games (I have a few private partial implementations of some old defunct game engines in-progress), the distinct lack of prior cases means, sadly, it's prudent not to release them at all while the companies are still active.