FWIW, that's great for your intentions with "open source code", but some people--like myself--in fact explicitly placed licenses on our code (and additionally did not even upload it to GitHub ourselves: our code is open source and of course anyone can edit it in public and redistribute it) that add "discriminatory" clauses as we aren't merely being purely altruistic: we are attempting to help provide code as ammunition in a war against developers who would attempt to lock users out of control over their own technology.
When you put your code under GPL (as I explicitly and actively chose to; or to put your content under something like the Creative Commons ShareAlike license, which I've explicitly used for many photos I've distributed over the years) you are purposefully choosing to help only those people who are willing to agree to the same level of open-ness in their products. And, as a reader, you know that if you read my code and "learn" from it, you are tainting yourself in a way that might make it difficult to later defend yourself from claims I might make.
To the extent to which it is legal for Copilot to train a model off my code as it might be fair use as some kind of transformative work, I want to be clear that I do not at all believe it is legal for someone to USE Copilot to write software that might be similar to my software... at least without having their lawyers carefully vet the resulting code it generates to determine that none of the expressive intent of my code has managed to leak through Copilot's attempt to launder my code as the user attempts to "autocomplete" something similar.