History shows when you forked from somewhere, not copypasta.

If you can copypasta a complex project with >dozens of active users and a commit history showing that you've made improvements to it over time, I'd argue that it's hard / pointless to distinguish that from actual programming. If you can ship working code, support it over time, and enough people appreciate what you've created to use it regularly / rely on it, why does it matter if some parts are even verbatim copied from SO or elsewhere? Thought experiment: compare this to using a library someone else wrote.