IANAL, but I have written licenses for that purpose. [1] (I'm trying to get them reviewed by a lawyer, but can't afford to; maybe I'll do a GoFundMe.)
What I did is say that if you feed copyrighted software to an algorithm that itself outputs software, then the license applies to the output. This covers the output of compilers and such, but it would also cover Copilot in my opinion. We'll see what a lawyer says.
However, even with a license, I wouldn't doubt that Microsoft would just put it through GitHub anyway because finding them out would be extraordinarily hard.
The “Yzena Copyleft License” states that it's a copyleft license, but it also states that it's not a viral license. According to Wikipedia, a viral license and a copyleft license are the same thing.
There is a difference between "strong" copyleft and "weak" copyleft. An example of "weak" (non-viral) copyleft is the CDDL. In fact, the CDDL's Wikipedia page talks about strong and weak copyleft.
You can read [1] for a breakdown of copyleft by an actual lawyer. Suffice it to say that Wikipedia's Copyleft page is woefully inadequate.
What I did is say that if you feed copyrighted software to an algorithm that itself outputs software, then the license applies to the output. This covers the output of compilers and such, but it would also cover Copilot in my opinion. We'll see what a lawyer says.
However, even with a license, I wouldn't doubt that Microsoft would just put it through GitHub anyway because finding them out would be extraordinarily hard.
[1]: https://yzena.com/licenses/