[mitthrowaway2]

Code is a more restrictive space than prose. Prose has to be grammatical and meaningful, but code has to compile and efficiently serve a useful specification.

The central idea of programming languages is that the grammar is very restrictive compared to natural languages. It's quite likely that, with the exception of variable names and whitespace, some function you wrote to implement a circular buffer is coincidentally identical to code that exists in Sony's or Lockheed Martin's codebases.

Plus there's the birthday problem -- coincidences can happen way more than you expect. And even with prose, constraints like non-fiction can narrow things down quickly. If everyone on HN had to write a theee-sentence summary of, say, how a bicycle works, there would probably be coincidentally identical summaries.

[harles]

Three sentence summaries probably wouldn’t qualify for copyright protection. The same should be true of code - if we think the standard for copyright protection is too low, we should raise the bar on complexity requirements, not throw out copyright.

Even if a programming grammar is more restrictive, there’s some length where things become almost certainly unique.

[edgyquant]

ReactOS actually got sued by Microsoft for stealing code and one of their proofs was a piece of code (can’t remember exactly what it did) that basically matched the same function Windows code with a few things changed.

It was ASM code I think, and their defense was that there was basically one way to write a function that does this.

[moyix]

I think you're misremembering here; as far as I know (and as far as I can tell from searching just now) MS has never sued ReactOS. There was a claim made back in 2006 on the mailing list that a portion of syscall.S was copied, and this caused ReactOS to do their own audit:

https://en.wikipedia.org/wiki/ReactOS#Internal_audit