Don, there is an easy way to wrap your head around this.
The car customers all paid for the development of the Mustang, no matter if they drove LTD's, Galaxies or Mercury Monterreys, the costs of designing that Mustang was spread out all through everything that Ford did during those years.
Then, when the Mustang came out, to the consumer it seemed to have been developed "for free". Then the car company copyrighted the name. (not all in that order, though)
The same things happens with things like the North American Sabre fighter,,,,,the customers paid the development costs when they bought the aircraft,,,,,the difference is that those costs were reported to the customer as we went, even if it was before the aircraft were being built. In the end, the product is copyrighted to the builder.
Unless we think that if the Government buys 1000 Magnavox Televisions, that all Americans now own part of the rights to the Magnavox name? (or Stanley tools, or Dodge trucks, or Zippo lighters?)