Hi,
“He made it so you could see it, but not touch it,” says Seaber. That is, while Seaber and others had the files they needed to have printed-circuit boards made, no one but NwAvGuy had the original layout file, which would allow easy changes."
Given it seems there is reasonable motivation — HiFi companies are selling his designs — it would relatively trivial to re-enter those designs in your EDA tool of choice, before modifying and issuing the files output under whatever licence you please (or not doing).
Agreed regarding "ND" but not so sure about the ethical issues around your suggestion. For me, it was this bit made me wonder if it was really "open source" as they didn't have the actual "source": only the manufacturing "object files" (gerbers?).
What do the Open Hardware peeps and licenses say about the requirements around the artifacts that have to be provided in order to be "open"?
Regards, @ndy