However, two things: you claim that Copilot might have infringed during training because of the GPL, but the GPL's clause only kicks in on distribution. If GitHub had trained Copilot and then did nothing else, that clause would not kick in.
Second, your Stack Overflow example of copying is not good because SO has an explicit license for all material given. You must agree to let SO and others have the material under that license, which is CC-BY-SA 4.0.
Don't get me wrong; I hate Copilot. But those two things you said were wrong.
I'm too lazy to check the GPL comment (I'll assume I made a mistake). But as far as I can tell my only reference to Stack Overflow was not about liability based on copying from SO. I was making a comment about a common industry practice.
Good paper, though I disagree with many points.
However, two things: you claim that Copilot might have infringed during training because of the GPL, but the GPL's clause only kicks in on distribution. If GitHub had trained Copilot and then did nothing else, that clause would not kick in.
Second, your Stack Overflow example of copying is not good because SO has an explicit license for all material given. You must agree to let SO and others have the material under that license, which is CC-BY-SA 4.0.
Don't get me wrong; I hate Copilot. But those two things you said were wrong.