I agree, the commercial/non-commercial options do need expanding. There should be more options, something like, 
      1: non-commercial, commercial use prohibited.
      2: commercial restricted, use in commercial renders allowed.
      3: commercial unrestricted, use as determined in readme. 

Obviously number 3 needs working out but it's just an example.
I think a lot of people (as pjz99 says) take the commercial/non-commercial tag when uploading freebies as implying resale or commercial redistribution allowed rather than use in commercial renders and so tag them non-commercial yet have readmes saying commercial renders ok.

To be honest, I don't download non-commercial as a whole (only the odd movie/comic items that I know can't be used commercially) even though I don't make money from my pics. I'd just rather have the option to be able to make money should the option arise without having sudden bouts of 'Oh bugger, does that item allow commercial or not?!' and having to worry about having to source and replace elements that don't.