It’s up to copyright holders to enforce their copyright. They can choose at any time to start or stop or restart doing so, for any reason, as long as the term of the copyright has not expired.

I’ll say this, if someone made a prediction market, I’d put down $10 on 70% odds that Microsoft won’t try and enforce in this case. They’re trying to reach out to developers these days, and suing Fabrice over this interesting project would piss off a lot of developers. But I accept the 30% odds that they may just pursue enforcement anyway.

In my opinion, Fabrice Bellard showing a VM in HTML5/JS with Windows 2000 is a great honor for Microsoft, not a harm at all, quite the contrary :-)