It's a stretch to say they used GPLed code. They wrote a kernel module that is unavoidably tightly coupled to the Linux kernel, which means that it must be GPL

It's a stretch to say they used GPLed code. They wrote a kernel module that is unavoidably tightly coupled to the Linux kernel, which means that it must be GPLv2 as a derived work. They appear to have intended to release it as GPLv2, it just took a while. The GPL does not require them to release the code on the internet publicly, just to release it under the GPLv2 to people who have received the code in some form (binaries) when they ask for it. Someone asked for it, and they provided it. They were decent about it. The only real 'violation' is that they didn't initially release the binary with GPLv2 license text. I forgive them.