When the recent Github v. youtube-dl fiasco happened, I remember reading similarly strongly-worded but dismissive comments regarding fair use, stating how it is quite obvious that youtube-dl's test code could never be fair use and how fair use itself is a vague, shaky, underspecified provision of the copyright law which cannot ever be relied on.

To me, seeing youtube-dl's case as fair use is so much easier than using hundreds of thousands source code files without permission in order to build a proprietary product.