Yeah, Nintendo here? What do you need, a lawsuit?

Nintendo would see the sky fall down before they would do something like this, because unlike idSoftware, who release good work, make their money, and move on, Nintendo would re-release the same stuff 5 times, except it’s always more expensive the next time

It would literally not hurt them to open source anything <= 3DS now after the eshop closure. The act of doing that and everything that would come of it (e.g. rom hacks) would actually be a pretty good PR move imo and maybe they’d even find new developers, acquainted with their code, that could be hired by them so they have developers that actually know how to develop good and optimized games.

One can sadly only dream.