I know on its face this looks like stealing, but this would likely fall under fair use, since the original work is being transformed.
Not a lawyer, here, of course, but does "transformed" cover making a functional copy? Artistically, "transformed" means something is related, but different. In the case of software, this transformation is to code that actually does the same thing as the original. Is that "transformed"? I apologize if that comes off as pugnacious - I'm trying to learn, not poke holes in your argument, but I couldn't figure out a better way to phrase it and still retain the question.
Functionality isn't covered by copyright; it needs a patent. You could even have identical files, if it's the simplest way to do something: https://en.wikipedia.org/wiki/Google_LLC_v._Oracle_America,_....
Previously a month ago on source: https://news.ycombinator.com/item?id=47350424