My guess is that the site is intended as a portfolio for an architecture student. The pictures are presented as downloads because (s)he's used Wordpress as a shortcut to getting the site online. Based on a quick peek at the source code I believe the galleries are a WP add-on called Quik Gallery.

I'd have to agree with the others and say that usage was not intended; there's no usage information because of inexperience on the owner's part, cultural differences, or both.

You could try postmaster (at) 3dhousedownload.com, or webmaster (at) 3dhousedownload.com if you want to try contacting him or her.