As an attorney and music lover, builder, and fan, I have to say that legally you are 100% correct on the issue of patent law, copyright infringement, etc. However, adding a dose of reality on the subject is necessary. If John Smith builds a beautiful guitar in his basement that looks similar to a Gibson or Fender, I highly doubt that the FBI is going to come knocking on your door. However, if you are mass producing knock-off guitars and claiming that they are authentic Gibson's or Fender's you will be in some serious hot water. Have fun building and remember that these laws exist to protect consumers and companies as well.
Ron Belluso is a founder and contributing author of http://www.wiser-rocker.com, an indie music career site.