This seems to be a regular question on most circuitbending or DIY electronics based boards.
I'm not sure that its actually possible to copyright a circuit design. You can copyright its presentation in a magazine or internet article or whatever and i think that you can copyright or patent the circuits inclusion in a specific product. On the other hand i don't know for sure, but it seems like there are a awful lot of TB303 clones that claim to use the exact original 303 circuit. You'd also think that what with there being fairly standard ways of building circuits like filters, that 99% of synths ever made would be infringing on some copyright if you could copyright circuits. Don't take my word for it though.
As for the ethics, theres always people that will moan about 'cashing in on the DIY ethic' or some such nonsense and its usually because they didn't think of it themselves. If i get sent something like a TR606 to modify it would be just stupid for me to start from scratch without first searching the net for every 606 mod i can find and trying them out. Obviously i might change the mods or come up with some of my own but essentially i'm making money out of someone elses time and effort finding the mods initially.
Now if you had the sole intention of just finding a way of making some money and had searched the net to find some kind of circuit you could use to make some quick cash, then it might be a different matter entirely.
Anyway, surely if its a DIY pedal company then all you are doing is selling something that anyone could just make themselves with a bit of effort, as the information on how to build one yourself is still in the same places that you found it. If i wanted one i wouldn't be buying one from you, i'd be building one myself probably using the same information you found. A lot of poeple don't have that option which is why circuitbenders.co.uk remains viable, which is why this forum can continue to exist and is why people want to buy your atari punk consoles etc. To be honest i was seriously considering doing the same thing but just don't have the time.
Basically i think that as long as you are not being rude about it or just taking the piss then its fine.
That turned into a bit of an essay
