Fair use is about more than just the size of the excerpt, and even open source software still has a copyright and terms.
If you write an article about good writing, and quote a choice paragraph from someone else's work to show an example, and credit that quote, that is fair use.
Is it fair use if you read an awesome paragraph, something that really is the result of the authors unique intellect and effort and craftsmanship, and makes you think "damn", and then drop that same jewel into your book?
You can probably get away with it, because you probably just won't be able to convince a judge that any single paragraph is that big of a theft.
But I don't mean to ask if you can get away with it, I mean to ask if it should be considered fine honorable behavior.
The difference is, the paragraph isn't being included for examination or comment or transformation, it's being included to directly copy and perform it's original function as part of what makes a work a great work, and, it's not being credited in any bibliography or footnotes or directly.
The reader reads the paragraph and is impressed by your deep insight, which you never had, and the original author did.
How about if your new book has many such uncredited snips from other authors, such that your new work is denser and richer than any of the other individual authors?
This is what copilot is doing, or rather it's facilitating people doing it, as far as I can tell.
The original snippets are functional, not there for examination, copied verbatim, not transformed (sometimes), and not credited.
Most of it comes from open source works anyway and most authors would probably be fine with it if the stuff was simply credited.
I think as a tool, in the context of software vs literature, the tool is probably more good than bad for everyone as a whole. It probably results in the generation of more, and more correct software. Since software is more like a machine than a novel, it benefits all of humanity when machines work well.
But it needs to somehow credit the original authors, or if that's not possible then users do not get to claim credit for any work it was used on. Or, they can only claim a sort of tainted credit.
Maybe it needs a combimation of policies that together make a fair system. One element would be, the training set must be composed of strictly open source software (pick some definition). Then another element would be, any work that uses it, is tagged as such. You only get to say "I wrote this, with copilot." not merely "I wrote this". And any work that uses it is itself gpl. The individual snips maybe don't have to be credited because the theory will be the training set as a whole was credited, and those are all available somewhere. You as a contributor won't get credit for being in someone's mp3 transcoder app, but that app WILL declare that it used the training set, and the training set WILL declare all of your material that is in it.
Maybe there can be a special version that only includes code where the original terms did not require anything at all, not even preserving the authors name or the license that says it's free, and that version's output can be used without credit.
If proprietary software wants to benefit from a tool like that, they can pay for licenses from other proprietary software developers to include their software in their ai's training set, just like with normal software licensing for inclusion and re-sale in a new product.
But right now, as copilot currently exists, as far as I can tell it's blowing past and ignoring ANY considerations like that and Github are simply outlaws.