From my understanding of a blog post by GitHub last year, they are planning to launch a tool to find similar code to what emitted by CoPilot, implying that CoPilot does not mix multiple sources for a single function, but derives a code block it found with a similar functionality (or maybe bigger blocks with similar functionality, IDK).
If CoPilot indeed derives a function (or a functional block) from a single source, it might plainly violate the license of the repository where it derives the code from.
There are many questions, and nothing is clear cut. The only thing I know is, I will never use that thing.
At what measure is one sufficiently inspired for it to be a derivate work? That is up to courts to decide.