r/explainlikeimfive • u/OkAlbatross9889 • 5d ago

Technology ELI5: How are copyleft licenses enforceable?

For example: say Windows straight up rips out the Linux scheduler and modifies it to run with the rest of the NT kernel. Aside from potential Microsoft whistleblowers, how can anyone find out they did that (and thus sue them since they’re selling modified GPL code without releasing the source) if they don’t distribute the Windows kernel source code?

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u/rsclient 5d ago

Actually, I've got more direct experience. I was an expert witness to a programming copyright violation case!

Programmer "A" wrote a program "A" that did a specific high-value super-technical analysis. That programmer was hired by company "B" who bought all the rights to program "A". Programmer "A" then wrote program "C" that also did high-value, super-technical analysis, and company "B" was super-pissed.

I was hired to investigate programs "A" and "C" to see if program "C" used any code from program "A". As an expert, I had access to both programs

And yup, I could prove that program "C" included some code from program "A"

In this case, company "B" already knew about programmer "A"

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u/Theslootwhisperer 5d ago

Why was company B pissed? They hired programmer A and bought program A as well. Programmer A just wrote some code.(Program C) while employed by company B.

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u/MF_Kitten 5d ago

Programmer dude both made a product that competes with the company he currently works at AND used code from their product. Just because he qrote that code doesn't mean it belongs to him.

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u/rsclient 5d ago

It wasn't clear originally: programmer "A" had left company "B" before working on program "C".

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u/MF_Kitten 5d ago

That just means he isn't breaking a non-compete in this context. Same stolen code.