Maybe it's because I'm only using it as plan B or C (after the documentation has already failed me), but I have never gotten any usable code out of chatGPT.
And yet co-pilot is able to finish my code perfectly after I type the first few characters... even though they're the same model.
I think co-pilot works better because it has the context of the whole project for reference when suggesting auto completion. I've gotten a lot of unusable junk from it too though
Not that I'm aware of. Even if the input is public data, the actual training scripts and resulting model tend to be closed-source. Meta's one of the only major companies I know of to release their models under a somewhat-open-source license.
ChatGPT is amazing for describing what you want, getting a reasonable output, and then rewriting nearly the whole thing to fit your needs. It's a faster (shittier) stack overflow.
I normally have it output toy examples of the syntax I don't want to bother learning and then remix that into what I need. IMO it's better than stackoverflow because stackoverflow code is more likely to be not really what you were searching for or not actually run because the author didn't bother testing it and there's a typo or something.