Oh Dave, I'd KILL for bootleg Star Wars in the U.S. that was half as nice as stuff like this. It just is dangerous water for a company to tread.
With militaria, they can copy without trampling on toes, so long as they don't directly copy licensed material, like plane names, vehicle names, historical character names, etc... Like 21st has the license to reproduce Gen. George Patton, which was rather expensive. As well as a license to repro Dodge products frm the war. I guess BBI has the rights to "Humvee" though.
Contrary to popular belief, these little licenses cost TONS to these small toy companies, and have much less/shorter earning potential than Star Wars does to Hasbro. In the end they're equally expensive, if not more so, but the companies shell out big bucks for them.
Plane names, squadron insignia, and I guess noseart are also all copywritten materials as well. I learned a lot from my long discussions with some of these companies over the years. They give you some really good insight into the industry that Hasbro rarely ever shares, and they give it to you from a truly costly perspective due to their size.