As interesting as this is, I don't know that this necessarily applies to us as prop makers. I feel like I need to voice my opinion in a decently long paragraphs of explanation, so tune in if you will.
When we, as fans, create our own models from scratch, by means of digital technology such as CAD , Zbrush or any other modeling program, or even by means of just building from scratch using cardboard and free handing it, we are entitled to our own legal rights as creators of our own handy work. No matter how detailed it is, our own created models will never be the exact replicas used by any big companies and/or movie producers, therefor I do believe that we aren't violating any copyright laws. Now, of course, if we were to use false advertising , claiming to be selling the original armor from the set of *insert famous movie here* then we would have issues with false claims, and other legal trouble could pursue. The only real issue I could see happening is the models being ripped from games, and then being created and mass produced. That could possibly create some sort of legal loophole that someone could use, claiming that "John Smith" stole the 3D work of So-and-so company that made this popular game, and got rich selling them for thousands of dollars.
This issue goes into a bit of a different direction, as this guy had the very first original helmet from the movies, because he did create them. Pulling casts of a helmet or re-manufacturing the helmet that is protected by copyright, such as this Stormtrooper helmet, is definitely illegal in my opinion. "...Ainesworth is the guy who manufactured the original Stormtrooper helmets for the Star Wars movies." He had the original, made copies of it, and sold it for thousands of dollars. When you take something that is as popular as Star Wars, a franchise that is worth an enormous amount of money, and you take a piece of, well technically by copyright law, "their work," then you are stealing from them in a way. Especially when you're making as much money as this guy did by selling them, you can't really expect to not see some legal trouble here. This is America, where you can sue someone for almost any reason you can think of.
In all, I don't believe we'll be having problems here at the 405th. Selling armor here in the classifieds for a fair price is one thing, but we're not selling original casts and molds of famous armor sets/pieces that we took from a movie set.