You don't need an ms account? I thought that's what the key gets tied too.
I upgraded my daughter's computer from Win7 32-bit OEM to Windows 10 64-bit, and everything worked fine,even though she does not have a Microsoft account. So I can confirm that you don't need a Microsoft account.
The conversion from 32-bit Windows 7 to 64-bit Windows 10 required me installing WIndows 10 twice. First, as an in-place upgrade to Windows 10 32-bit. Once this was activated I did a clean install to Windows 10 64-bit. The 64-bit "found" the previous activation and used it. I'm not sure how it found the activation - it either found it on the hard disk, or it may be tied to the hardware, and just re-activated the same hardware online. I'm not sure, but either way a Microsoft account was never involved.
My daughter already has a Google and Apple account - didn't really need a third one.
Out of the 10 computers at my house, I've moved 5 of them to Windows 10 (one is a tablet). It didn't not go smoothly in all cases, and I had a few hours of frusteration, but in the end all systems are working fine. I still think Windows 7 "looks" better, but can't complain all that much. The App store is not really much better, so I continue to ignore it (even on the tablet) but at least it's easy to do that. Two of the systems are "work" systems, so I installed CliassicShell with the 2 column start menu option, and productivity is fine.