I think the purpose is the intent. If the source code to Microsoft Windows is illegal, is the source code plus one bit of padding at the end illegal? How about

I think the purpose is the intent. If the source code to Microsoft Windows is illegal, is the source code plus one bit of padding at the end illegal? How about two bits? How about an XOR transform with some random number, which I also publish online? How can Microsoft copyright an infinite number of variations of their source code? The answer is that they obviously can't, but all those variants are illegal if the purpose is to get back to that same source code. If you're transforming their source code, and providing some obvious or non-obvious key for how to get from your transformation to the original, you're violating copyright.