[CM30]

Well, the decomp requires you to provide your own ROM, and doesn't include any of the assets from the original game. So, that's probably okay for the most part.

This browser based version on the other hand, is in far murkier territory. The fact you don't need a ROM means the assets are definitely included by default on this site, and Nintendo would have a way better case for getting it taken down.

It's basically equivalent to those ROM sites that let you play GBA ROMs in the browser through an emulator written in JavaScript or WebAssembly.

But Nintendo's lawyers pay a lot less attention to anything prior to the Switch generation, and the same presumably goes for the Pokemon Company ones. If this project gets a lot of media coverage it's probably toast, but if it's mostly discussed on the odd programming forum like this one, it could survive a very long time.