From: Oslo, Norway
Interesting site, and some classics there for sure. I tried to have a look at the code to see if they might just be leeching off the Internet Archive, but looks like they host the stuff themselves. It's certainly faster than the Archive, that's for sure.
As for legality... well, it's murky waters. On the surface, they're not doing anything else than the Archive is doing with their emulated DOS/Amiga/C64/AppleII games. But there are some games there I definitely think are not out of Copyright, like Civilization, Steel Panthers (still owned by Matrix?), Worms or Diablo (Blizzard could hit hard!), and the console game publishers are known to be nasty with protecting their IP no matter what. So I think they're likely operating on the illegal end of things and just hoping to not get noticed too much.
Then again, most of these publishers are long gone and some, even if they still own the IP, will probably not care a bit about it. Like MicroProse, their games are probably still owned by Atari but again I doubt they care much. And the site says it will take down any game it receives a legal notice for so that's the "DMCA" sorted (possibly...)
I've used several of these Abandonware sites over the years, but sadly they all tend to disappear after a while. Either for legal reasons, or simply because it costs a lot of bandwidth to run a popular site with downloads. Mostly they die for lack of money to cover bandwidth costs, or lack of time or interest to maintain and support the library.