This shit is somewhat agreeable now, because Pal World is so similar, but once this door is opened, it's never going to let developers have the freedom to invent and innovate, because crusty old bullies want to use the legal system to punish anyone that dares resemble 2-3 decade old game mechanics.
Should platformer games pay royalties to Nintendo for having the first character to jump twice it's height?
Video game companies rent seeking for "game mechanics patents" on old shit is just ironically anti fun.
I don't think that you can patent game mechanics in the US, have read about that before, but it sounds like this lawsuit is in Japan, and their IP system may not work the same way.
EDIT: Sorry, I'm wrong. It's that game rules aren't covered by copyright, that's what I was remembering.