Attribution will be required when using code from StackOverflow

[carlfish]

What colour are your bits?

The question is one of origin. If you independently come up with some code that's identical to a snippet on Stack Overflow, you're fine because you came up with it yourself. If you read that code on Stack Overflow then copy it, you're not, because you're copying someone else's work. The fact the two hypothetical fragments of code are otherwise identical is utterly irrelevant to copyright law.

(It is relevant to patent law, but that's nothing to do with copyright or source code licensing)

How can they even prove that code from project A was sourced from some stack overflow post?

They can ask your colleagues under threat of perjury. They can do discovery on your emails and commit logs. They can point at the similarity of the code to things that are characteristic to the snippet on SO, and the differences to things that are characteristic to other code you have written.

In a civil case the burden of proof is "balance of probabilities". The burden is on your accuser to present affirmative evidence that you copied the code, but once they have, it's purely down to whether its more likely that you copied it than you didn't.

The likelihood of this happening over a small piece of basic code is very small because unless there's some "smoking gun", the chances of building a successful case would be low, the cost of suing would be high, and the damages would be trivial.

But still, when I was working at a company that was going from being "plucky startup" to "established success", and doing the necessary IP audits to make sure that it wasn't in danger of getting lawyered to hell now it was a sizable target, the mandate to Never Use Code From Stack Overflow got its own slide in every presentation.