I don’t know about the legalities, but according to Apple you are only allowed to run macOS on real Mac hardware. Anything else is probably an EULA violation or something.

As an aside, in the script you link to is this line

> VBoxManage setextradata "${vm_name}" "VBoxInternal/Devices/smc/0/Config/DeviceKey" "ourhardworkbythesewordsguardedpleasedontsteal(c)AppleComputerInc"

I think that’s Apple’s way of reminding you about their rules regarding host machines.