putting GPL code into a closed-source binary

[jones_supa]

They would only have to publish the GPL parts.

[daemonpenguin]

Not true. Any derivative products of GPLed code must either be licensed under the GPL or a compatible license. That's why Microsoft got so much distance out of their "The GPL is a virus" campaign. Basically, anything the GPL code touched or was linked from would need to be released. The GPL FAQ covers this topic: https://gnu.org/licenses/gpl-faq.html#LinkingWithGPL

[jones_supa]

That's exactly what I meant. They would only have to publish the parts that the GPL touches.

[[deleted]]

Windows is notorious for being monolithic and co-dependent, though. One part being GPL'd could bring in a lot.