I've sent a note to 3d.sk asking if they will clarify their terms of use on the photo references.
Specifically asking about non-commercial use in free sets.

We do pay for those photo references in order to use them in texture making so it seems it should be allowed.

I'll update this when I hear back from Tomas.

Let me introduce you to my multiple personalities. :)
     BluEcho...Faery_Light...Faery_Souls.