You mean this which was applied back in 2014 for Windows 8.1 and still applies to Windows 10 and the IoT version of Windows 10 or do you want the source... here you go. Please note, before you go into a semantics fueled discussion; this applies to Windows 10 as well, which was a free upgrade from Windows 8.1 and inherited that "below 9 inches" criteria for a free license, but same EULA for usage. I've honestly no clue how the license applies to every hardware manufacturer though.

Very keen difference here and you're right. You still get a license but it's free. You still fall under their EULA if you activate the installation. But if you receive a device, install Linux on it, never activate the Windows EULA/license; you are fully under the license of whatever distro you've installed. Now... the question about warranty is up to the manufacturer. But who worries about warranties when you're installing Linux on a device that's built for Windows?

Normally... not I.

You have to always understand that the EULA is for the OS and has to be activated. If you do not agree to it, then there are other devices that do not seem to care about the choice of OS - Dell XPS 13 Linux/Dev Edition for instance is modern equipment sans Microsoft's Windows license & EULA attachments. And all drivers for the device work with Ubuntu (for instance) without any issue.

I think a smarter question would be if that situation is the same with the GPD device. And to be honest, since they're Chinese, they probably are OS agnostic and don't follow the EULA to the letter. Call it a hunch.