I think that's probably an interesting case, and whether it's a valid defence is going to depend on what you're doing. If you are (for example) shipping a prod

I think that's probably an interesting case, and whether it's a valid defence is going to depend on what you're doing. If you are (for example) shipping a product which is effectively a thin wrapper around a GPL 'd component, but instead of linking to a GPL'd library you've written and dutifully GPL'd a small shim program that turns the library into an executable and reads function arguments over a pipe, then you call that from your 'non-GPL' code... I don't think you'll find the process boundary is some sort of absolute defence in law. In fact you may be looked upon unkindly in court for having knowingly attempted a license circumvention mechanism. The law is not necessarily sensitive to the exact inner workings of a turing machine, and the definition of a derivative work may or may not be affected by such shenanigans.