Can you explain why you think this is covered by fair use? It seems to me to be
1a) commercial
1b) non-transformative: in order to be useful, the produced code must have the same semantics as some code in the training set, so this does not add "a different character or purpose". Note that this is very different from a "clean room" implementation, where a high-level design is reproduced, because the AI is looking directly at the original code!
2) possibly creative?
3) probably not literally reproducing input code
4) competitive/displacing for the code that was used in the input set
1a) Fair use can be commercial. And copilot is not commercial so the point is moot.
1b) This is false. This is not literally taking snippets it has found and suggesting it to the user. That would be an intelligent search algorithm. This is writing novel code automatically based on what it has learned.
2) Definitely creative. It's creating novel code. At least it's creative if you consider a human programming to be a creative endeavor as well.
3) If it's reproducing input code it's just a search algorithm. This doesn't seem to be the case.
4) Most GPLed code doesn't cost any money. As such the market for it is non-existent. Besides copilot does not displace the original even if there were a market for it. As far as I know there is not anything even close to comparable in the world right now.
So from my reading it violates none of the guidelines.
1a) commercial
1b) non-transformative: in order to be useful, the produced code must have the same semantics as some code in the training set, so this does not add "a different character or purpose". Note that this is very different from a "clean room" implementation, where a high-level design is reproduced, because the AI is looking directly at the original code!
2) possibly creative?
3) probably not literally reproducing input code
4) competitive/displacing for the code that was used in the input set
So failing at least 3 out of 5 of the guidelines. https://www.copyright.gov/fair-use/index.html