Point is that you can ask 100 programmers to write an average function and probably most of them will come up with this answer verbatim. How can copyright law handle this? There is also the opposite problem, I can copy a complicated snippet and change the variable names. Am I absolved from liabilities now?
If they come up with it on their own, it shouldnt be an issue. Likewise, swapping the variable names does not absolve you from liability.
Copyright really is not only concerned with what exactly is on the page, but also how you got there, and where the knowledge came from to get you there.
What if I read your codebase, and then years later while programming for myself I inadvertently use solutions you came up with while thinking I came up with it myself?
There really are no hard set rules, and this is something that is handled on a case-by-case basis based on whether or not a convincing argument can be made that you copied a novel idea from someone else and claimed it as your own.
We can argue the semantics of it all we want, but the subject area is an active battleground. Typically it only matters when money starts to get involved, since no one usually presses the issue or gets involved with random personal projects. So when an enterprise level company leverages that lack of caring into a proprietary pay-to-use project that operates by copying and pasting code from copyrighted material, then it seems like a case might be able to be made for it.
