Just about anything online, is good for about 5 years at most, legal or otherwise.
Case in point, remember when online Journals were the rage? Then Blogging was the thing to do. Now it's Twitter, and how long will that last. MySpace and Facebook, yawn it's already sounding old.
My NDS rom site of choice proudly proclaims 'since 2006'. Oh like that means anything hehe.
The first Nintendo rom site I discovered is currently just magnet for automated porn spam fishing. No idea where the site owner went, but my guess is involved legal threats and maybe even repercussions.
But the thing is, posting links to sites is not the crime, actually hosting the file is where it gets risky.
Granted, it seems GBAtemp prefers to not even offer the links to the offsite locations. Makes a kind of sense. Although if I was Nintendo, or someone like them, chances are I would have strong armed someone a long time ago to turf GBAtemp, even if there are NO files hosted here.
Because it hosts a community that essentially is a teaching facility for all you ever wanted to know about using the data you downloaded, which is essentially an illegal dowload in most cases, which is generally acknowledge as illegal in enough countries to matter. I mean, the fact that I as a Canadian CAN legally copy anything I bought, won't help you in another country where it is NOT legal.