This is a great point. If I recall correctly, prior to Microsoft's acquisition of Xamarin, Mono had to go out of its way to avoid accepting contributions from anyone who'd looked at the (public but non-FOSS) source code of .NET, for fear that they might reproduce some of what they'd seen rather than genuinely reverse engineering.

Is this not subject to the same concern, but at a much greater scale? What happens when a large entity with a legal department discovers an instance of Copilot-generated copyright infringement? Is the project owner liable, is GitHub/Microsoft liable, or would a court ultimately tell the infringee to deal with it and eat whatever losses occur as a result?

In any case, I hope that GitHub is at least limiting any training data to a sensible whitelist of licenses (MIT, BSD, Apache, and similar). Otherwise, I think it would probably be too much risk to use this for anything important/revenue-generating.