In answer to your questions... 

"...the market one what is the licence on this item?" 
You would have to ask that store. That product isn't sold at r'osity. "

Would the artist that did the original model that this is a copy not have something to say?" 
For the freebie it's Artists. The freebie model was originally made by a Mr Procter who had the model on his Movie Mesh Site. 

The model was 'poseried' by Numanoid aka Helgard. I made the maps for the poser version. If the product was a copy of the freebie we would've complained. But as I understand it the product is an original mesh (the maps certainly are) so it's not a problem from my end. 

"After all if I pay for it then I could use it in commercial work." 
Nope. Muralist and kuroyume0161 are correct. 
The reason 'our' APC is free is because the design belongs to Paramount. 

The consesus seems to be studios will tolerate fan arts as freebies, try to make a few bucks from it and they get unhappy. Keep it free fans get toys to play with, and lots of folks here like making fan art, studios get free publicity. everyone wins. Simple as.

Pinky - you left the lens cap of your mind on again.