Ide be more concerned with:

1)What are you using it for and are you getting any moeny for this model.

if you are using this model in aoint to sell something the modeler shoudl be given money or a share of profits. If you are using it for pure educational purpses i see no problem with it.

You could be a bit more specific on what your doing... just so you dont rip off some pore modeler...