I've also noticed it gone; it's a shame. In fact, there were some news stories about it some years back:Does anyone know what's up with the NS Dry Fly website? I've checked it a few times over the past month and it hasn't been opening. Hopefully it isn't gone for good.
Sometime after then Mr. Donoghue must have re-uploaded it. It was a lovely resource. I'd be glad to contribute to its re-post.