The CIC on the SNES is a different one, turns out it was already reverse engineered during the lifetime of the product.

You're right that it's a different one, but the patent's still expired. I was confusing the Rabbit with the more generic SNES CIC clones, though.

I am asking a legitimate question here that is not explicit in the article.

They say they are using a CIC chip from a supplier other than Nintendo.

Hi! For the legal aspect the other comments have already answered with loads of details (thanks!).

But to answer your question more precisely, this game uses the CIC chip alternative made by Infinite NES lives: http://www.infiniteneslives.com/snessupplies.php

This is one of the several CIC alternatives available, including the most popular that is the open-source SuperCIC chip: https://sd2snes.de/blog/cool-stuff/supercic

Seems like someone up above answered your question: https://news.ycombinator.com/item?id=23366883

Is it legal?

Keep in mind that legality only matters within a jurisdiction and that everything is illegal somewhere and at some scale, privately doing this is almost never illegal but doing it at industry scale would be. Next, try asking your lawyer if the factual law has much sway over the commonly shared understanding of the law (in a lot of countries it does not (e.g. you cant insult the monarch in most constitutional monarchies according to the exact word of the law, however this is not enforced nor cared about). Lastly, its only really legal till Nintendo throws enough money at it being illegal (there is no money in it for them, unless its about brand protection).

To conclude: the real answer lies in that the presets given from the Atari vs Nintendo case in America state that clean room reverse engineering of these chips is legal.

PS: IANAL, also gameboy games would be a trademark violation because of the security involving the nintendo logo being rendered on the screen by the cartridge and then being compared to one from ROM, a personal fav trick from nintendo also physically applied on the disks of the famicom disk system which held the nintendo logo on them physically indented allowing a stamp inside the disk reader to be inserted into it (easily bypassed by great groups such as hacker limited by simply adding a flat piece of plastic to the 2.8 inch quickdisks, or sipmly adding instructions on how to add this yourself).

A lot of this gets bypassed using ye olde method of selling the means and then making the user do the bypass themselves using the means.

> gameboy games would be a trademark violation because of the security involving the nintendo logo being rendered on the screen by the cartridge and then being compared to one from ROM

This is legal. It's analogous to the TMSS mechanism used by Sega in the Genesis; Sega v. Accolade [1] established that a "trademark violation" which the trademark holder forces to occur through technical measures is not, in fact, a violation.

[1]: https://en.wikipedia.org/wiki/Sega_v._Accolade

I think the CIC chip would be clean-room [1] designed in this case. It's been done with the Nintendo 64 chip as well via decamping-microscopes. [2]

[1] https://en.wikipedia.org/wiki/Clean_room_design [2] https://www.youtube.com/watch?v=HwEdqAb2l50

[2] includes the explanation of why its legal, the atari vs nintendo lawsuit.

If the patent is expired, why wouldn’t it be legal?