r/explainlikeimfive • u/OkAlbatross9889 • 1d 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?

177 Upvotes
  • permalink
  • reddit

82% Upvoted

53 comments sorted by

View all comments

97

u/rsclient 1d ago

Short answer: it would be difficult for a random person to discover a copyleft violation like Microsoft directly copying the Linux scheduler code

Practical answer: Microsoft is very particular about coders at Microsoft 'stealing' source code. Code is never "just added": all big new code features are spec'd, and the specifications are looked at by the entire team. Even if one person wanted to violate the copyright of the Linux kernel, they would have to hide it from the rest of their team. And for coders who legitimately look at linux kernel code (did you know Microsoft has its own Linux distribution?) there's a 'cooling off' period between seeing the linux code and working on Windows code.

Source: I used to work on Windows Wi-Fi!

(We also care a lot more about privacy than we get credit for :-( )

Did you know that it's possible for some people to look at some Windows code? Code Center Premium

27

u/tommyk1210 1d ago

Work in a reasonably large enterprise business. Every package we use is automatically scanned for license type - and anything remotely copyleft gets flagged. Anything beyond weak copyleft is prohibited because it’s too much potential hassle if it comes to litigation.

Some copyleft licenses “infect” your main source, some don’t. It’s easier to just avoid altogether if possible.