Re: principles of circuit different from tracing the circuit
While copying and selling actual artwork without permission is a copyright offence, the word 'artwork' when referring to a circuit layout does not imbibe it with the quality of being. an artistic expression, it's just a trade term to distinguish it from other representations of the circuit. You'd likely have to go some length to demonstrate your physical layout schema deserved protection under that legislation. While there may be ethical considerations about such practices, you are most likely copying pretty much the most obvious way to physically manifest the circuitry idea, and as the component count is mostly countable on my hands, and those components often have a tiny number of connections, that's likely to be a pretty obvious implementation.