The whole goodwill legal doctrine exists as a name recognition benefit. If someone changes a wire from one side of the input jack to another then claims copyright thats unproductive. I must take a stand here and say this; if the design existed previously in 80% of it's incarnation then it does not violate any responsible definition of reasonable behaviour. That makes me a bad guy I know but it's time people began concentrating on creating instead of hoarding. All amplifier designs that borrow from the past and just re-organise existing technology are free and open to use by all. Will that prevent people from designing because it will not be a lockin for their bottom-line? Naah; never has before. In fact; before the deluge of protectionist legal restrictions extended to any tiny re-design effort there was more creativity in the design arena. Thats the side I am sorry to say that seems correct to me.