I contacted the owner, and he replied that I can use them for my project, even if its commercial.
He just wanted some sort of link back to his site.
So...rather than spend dozens of hours making my own, Im going to use the Hard Vacuum set for a project I have in mind.
Thing is the whole set is geared to 20x20 pixel tiles, and Ive just about got the set prepared for use in Construct, but the mapping process is going to be a nightmare.