If you pay for a private copy or redesign of anything, you are not guilty of anything. If you make anything to the specifications of a customer, you are not guilty of anything. If you take a design or technical innovation of someone and make copies to make profit while not compensating the person for their hard work and ideas, you are guilty of something.
Making anything for yourself is making something for yourself. If I could make a blade to replace the one in the knife I like to have a better steel, I have done nothing wrong. If I modify my Windows 7 OS to make my computer how I want, too bad for MS. I have done nothing wrong as long as I don't resell it. If I put a better fuel injection system in my car, too bad for the car manufacturer as I have done nothing wrong. If I paid for it, it is mine to do what I want.
As far as the comments go such as "Any self respecting knife maker would not do this", I translate that to say "Any stuck up self important artiste would not lower themselves to help a customer". I have no problem if someone does not want to do something, but to evaluate their decision as being a moral decision is a bit much.
