For finished work its probably best to give credit to 'them' as well for anything that you use, even if it is an ear LOL.

Its great that youve taken the intiative to use any mesh for rigging as all meshes are different and you'll be able to decide what works best for weighting ie: meshes with good topo for deformation and also bad topo, you'll be able to see the differences, and able to make the changes accordingly.

cheers
Jay