It's not copying open source code. If you learn an algorithm to balance a binary tree from reading GPL code, and then go use that algorithm in your own closed-source project, with your own variables and types and context, are you breaking GPL? You're not copying the code. Just because you learned about it from reading GPL code doesn't mean that whenever you write tree balancing code from now until the end of time, all that code has to be GPL'd.
Copilot learns the "shape" of code. Common patterns and algorithms, etc. You can't copyright an algorithm.
If you decompile runtime bytecode and assign your own variable names, does the copyright of the original source code no longer apply?
If you trace a picture and use it in your work of art, does the copyright of the original picture no longer apply?
If you copy a tune but set it to new instruments, does the copyright of the original tune no longer apply?
Sampling is a legal minefield in music, why would it become less of a minefield in code just because you've automated it? So far the best attempt at an answer about the legal issue of Copilot I've seen was that it's "not technically violating copyright", which honestly is not very reassuring and extremely morally inconsistent for a company built by a guy[0] who is philosophically invested enough in intellectual property as the pillar of human society to write An Open Letter To Hobbyists and use his Foundation to convince entire governments of adhering to IP laws instead of allowing the mass production of vaccines and medicine.
[0]: Yeah, I know that he no longer serves an active role in the company but this was very much a founding ethos and this is at least a fair bit hypocritical.
If you teach someone about music theory by listening to Stairway to Heaven, and then they write their own song that starts with an A minor chord... are they violating copyright of Stairway to Heaven?
Copilot isn't sampling. Sampling is literally copying snippets of someone else's music and putting it into your music. Copilot doesn't do that. There's no giant database of text that it just slurps suggestions out of.
Copying of code needs to be very direct. Even Google copied tens of thousands of lines of code from Oracle character for character and won the case taken all the way to the Supreme Court. When Oracle made changes (even during the court proceedings), Google kept copying the code and every change Oracle made. So I doubt you’re at real legal risk with what you were proposing.
Is your argument in good faith? Seems like you know enough about the matter to destinguish an API definition from implementation. That's what that ruling was about, and you seemed to know it, yet make the comparison as if it was valid.
...and not compensating (or even attributing as required by the licenses) the authors for it.