Context:
Permissive licenses (commonly referred to as "cuck licenses") like the MIT license allow others to modify your software and release it under an unfree license. Copyleft licenses (like the Gnu General Public License) mandate that all derivative works remain free.
Andrew Tanenbaum developed MINIX, a modular operating system kernel. Intel went ahead and used it to build Management Engine, arguably one of the most widespread and invasive pieces of malware in the world, without even as much as telling him. There's nothing Tanenbaum could do, since the MIT license allows this.
Erik Andersen is one of the developers of Busybox, a minimal implementation of that's suited for embedded systems. Many companies tried to steal his code and distribute it with their unfree products, but since it's protected under the GPL, Busybox developers were able to sue them and gain some money in the process.
Interestingly enough, Tanenbaum doesn't seem to mind what intel did. But there are some examples out there of people regretting releasing their work under a permissive license.
I've seen busybox in a lot of software that's not free. One notable example is VMware. It runs on top of esxi as a package to provide command line functions to VMware hosts.
I'm pretty sure (IDK, I don't do development for vmw) that it's running on top of VMware's kernel, and they have binaries that you execute from busybox that interface with the vmkernel to accomplish things.
I don't have all the details and I'm far from an operating system guru/developer/whatever. I think that's permissible under copyleft, since they're not running things that you paid for on top of busybox, but I have no idea. I'm also not a lawyer, but they've been doing it forever, as far as I know.
Does anyone know more about it? I'm just surprised that smaller fish have fried for infringement, but someone like VMware is shipping busybox without reprocussions.
Maybe it's not busybox? Maybe it's something that just looks and acts like busybox? Idk.