> Would it be 'fair use' for the devlopers to simply copy code from those repos - even just 10 lines, and claim 'fair use' - i.e. circumventing Copilot?
Only a lawyer (and truly, only a court) could answer that question.
If you copy 100 lines of code that amounts to no more than a trivial implementation in a popular language of how to invert a binary tree, it's likely fair use.
If you copy 10 lines of code that are highly novel, have never been written before, and solve a problem no one outside the authors have solved... It may not be fair use to copy that.
Other people who have replied have mentioned "the heart" of a work. The US Supreme Court has held that even de minimis - "minimal", to be brief - copying can sometimes be infringement if you copied the "heart" of a work.
Only a lawyer (and truly, only a court) could answer that question.
If you copy 100 lines of code that amounts to no more than a trivial implementation in a popular language of how to invert a binary tree, it's likely fair use.
If you copy 10 lines of code that are highly novel, have never been written before, and solve a problem no one outside the authors have solved... It may not be fair use to copy that.
Other people who have replied have mentioned "the heart" of a work. The US Supreme Court has held that even de minimis - "minimal", to be brief - copying can sometimes be infringement if you copied the "heart" of a work.