Yeah, the Nintendo hardware fell out of copyright protection a few years ago and why we see so many weird NES compatible hardware solutions on the market now (like what's up with that handheld one?).
As a creator, I think the most important thing for something like this is someone enjoying it. Yeah it was a lot of hard work and time, and it would of been sweet getting some kick backs for it, but it started out as a labor of love and a hobby. If Redrum is getting credit for the work he put into making the game, I think it's alright (not fair, but alright). I mean, if I hacked Actraiser into some weird Dracula conquering Europe game where I had to go and destroy all of the "heroes" or whatever, it would be because I though the idea was cool and that people would like to play it, making money off of it never being part of the equation (though it does make for an interesting resume piece...).
Not to discredit anyone's concerns on the matter of financial compensation, but copyright of the original code (there is such a thing) and trademarks for the IP make it sticky as to whether Redrum would have to face legal ramifications if money were made off of it. However, if Redrum did not want his work put on cartridges and sold, I think he still has enough legal pull to get them to stop distributing his work completely.
Um...where was I going with this again? Oh well! Long story short; while monetary compensation for your work/hobby is nice I think the most rewarding is people playing it and enjoying it.