i think that any formal violation of an open source license would be very bad in terms of public relations - even if they can claim fair use.
Anything generated by copilot, which if it is a derivative work, is not something that copilot can hold the copyright on.
From the auditor's perspective it doesn't matter if you copied it out of stack overflow, from some GitHub search, or copilot. You, the human, didn't check the license / plagiarism detecter. It is you, the human, claiming copyright on the work you are creating which may incorporate material from other sources.
Copilot isn't claiming fair use.
You could argue that the model that copilot runs from is a derivative work (and this is going to be interesting when it gets to the courts, because, frankly no one will come out the 'winner' on this when trying to explain it to a judge) - but that's not the code that a human is claiming to be their creative work and is ultimately the license violation.
Personally, I (not a lawyer), believe that copilot is on ok ground - but anyone using it needs to do their due diligence in verifying that the code that they've incorporated is licensed appropriately - just as if they've copied something from Stack Overflow - who knows where that copied was copied from.
I have less concerns with identifiable code from copilot than humans not caring about the licenses of their source material in creating human generated content.
I think that's the part that people who don't think it's worth the money aren't getting. This kind of system is godsend for the likes of Infosys, TCS etc. So the immediate threat is to the jobs there - but the side effect is that it'll make it all even cheaper, so we'll see more "outsourcing to the cloud", so to speak. Often to the obvious detriment of quality, but that doesn't seem to matter in this market.