A neural network can only construct something out of things it has previously been given as input. So you could say everything it outputs is something that already exists. You could ofc say that makes sense, because there are only so many keywords in a programming language. Some pieces of code might be too small to be copyrightable or might be commonly used techniques.
But it's impossible to check the output to verify the source of any part of the output, so you never know if the output is legal to use in anything other than a personal use project you don't release

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