The basis of the GPL is copyright, so what you're really asking is whether you can use part of a copyrighted work in another work without infringing.

And the answer as always is "it depends".

If I use Copilot and it suggests a large block of GPL2'ed code for my project, which I then include, then that is a GPL2 license violation.

Whether the GPL2 will hold up in court, or whether the courts will uphold this specific case (e.g. can you prove intent? Do you need to?), is a separate issue entirely.

The next question is, can I use GPL'ed code in my product and then claim that it was injected by Copilot to avoid repercussions of my actions if caught?

> If I use Copilot and it suggests a large block of GPL2'ed code for my project, which I then include, then that is a GPL2 license violation

Not necessarily. Even 11k lines of copied code might fall under fair use, as Oracle recently discovered ;)

> If I use Copilot and it suggests a large block of GPL2'ed code for my project

But why would copilot do this? It's a language model not a database.

The claim (which I'm not qualified to judge) is that this use falls under fair use. The point of fair use is to allow some use of copyrighted works even if the copyright owner does not license it to you and even if the owner is explicitly hostile towards your usage. If it is indeed fair use, then the license doesn't matter because that's not the thing that's allowing you to use the work.

There are plenty of SAAS that use GPL'd code on the backend. That's fine.

You mean like Red Hat Enterprise Linux, that kind of commercial product based on GPL'd code?

Yes.