I feel like you're missing the forest for the trees here - making code freely shareable and remixable is exactly the purpose of GPL and other free-software licenses, but you can bet that the proprietary codebases Copilot will be used in will go out of their way to prevent any such uses of _their_ particular code snippets.
IMO, the only way to use Copilot's output in an ethically sound way is to only use the output it produces in AGPL licensed projects (assuming that Copilot has not been trained on any non-free software codebases which in itself is a strong assumption).
> IMO, the only way to use Copilot's output in an ethically sound way is to only use the output it produces in AGPL licensed projects
Even then, that is missing attribution which should really be the default for all code reuse and derivation even when you legally are allowed to omit it.
Based on this comment, you may not understand what the GPL's purpose actually is, because it is NOT simply for the promoting sharing and remixing. The GPL is for ensuring that code, and its derivatives, are all able to be shared and remixed in perpetuity. the biggest (imo) difference between GPL and MIT/BSD licenses is that you CAN NOT use GPL'd code in a non-GPL* codebase. (*or GPL-compatible license)
IMO, the only way to use Copilot's output in an ethically sound way is to only use the output it produces in AGPL licensed projects (assuming that Copilot has not been trained on any non-free software codebases which in itself is a strong assumption).