The Linux kernel is also in the free bsd project. I'm allowed to copy as little or as much of the kernel as I like into my personal project thanks to the GPL.

The Linux kernel is also in the free bsd project. I'm allowed to copy as little or as much of the kernel as I like into my personal project thanks to the GPL. Being able to attribute the source of a line of code doesn't help you to know if a repository can be legitimately hacked on. As you could imagine, I might just take all or part of the Linux USB stack from the kernel to retrofit it into my own kernel.