Apparently the webhost went bankrupt
I think it would be easier if you had a list of what is needed (on the wiki of UG maybe? so that it can be updated when needed) and then people look if they have anything.
Btw, as far as I remember, most of the downloadable content there (i.e. not the reviews) was gathered from some IRC channels (things like #oldgames on Efnet, Undernet and such). It is probably still there.