Eh, that's a bit of bullshit; I've seen floss Mario/Puzzle Bubble/Pang and such since forever and no one was sued.

Heck, back in the day Rogue was propietary and commercial (and thanks to that we got both the roguelike genre and the Curses library) and yet Hack was born as a libre clone and from Hack we got the now uber known Nethack and forks like Slashem.

Cloning commercial games it's older than Windows 95 itself and probably as old as the NES.

The https://osgameclones.com has so many examples that you whole point gets invalidated since the first Hack release for Unix. And Tetris for Terminals, MSDOS and the like.

Hell, in the 90's everyone in Europe (children of blue collar workers) got a Russian Tetris clone -oh the irony- called Brick Game with often several micro low-res commercial game clones such as for Frogger and Battle Tank. No one sued that company ever, even if the Tetris concept itself was for sure patented and copyrighted. And that game was probably sold by millions, maybe even more than the Game Boy if we count every clone sold with different plastic cases, because you could get one for the price of a book and today for less than a fast food ration.