It's one of those funny MS moves. "You can upgrade, because we want you to feel teh shinyness, but it won't be legit".
What's 'funny' (and not as in funny ha-ha) is that Microsoft is refusing to comment on what the differences will be experienced by the user of a legitimate vs. non-legitimate license.
It's very weird all the way around. If you aren't legit, you can upgrade, but it won't be a real upgrade and we refuse to tell you why it won't be considered to be or what the ramifications of that will be.
First of all yes, I didn't mean haha, I meant "playing a very complicated game".
If it's "proven" (and let's pass for a moment on false positives) as a non-legit copy, that gives them room to do all kinds of weird things to the very limits they think their $1000/hr legal team thinks they can get away with.
Is MS allowed by law to install their own custom spyware and snoop the address/other contact info of a "non-legit" user? Could they then wrap all of that into a package with a bowtie and feed it to a police force?
So then it gets all meta - why would a non-legit user WANT to upgrade? What do they get out of it? Wouldn't they sniff out that there's got to be a trap in there somewhere?