Did some digging, and found that the thing has some sort of expiry date attached to it.
C:\Users\Username\AppData\Roaming\Modiac\Blu-ray Ripper:
[General]
...
regUser=Giveawayoftheday@modiac.com
regCode=************
regExp=2012-03-07
I've set my computer's clock past that date, but it doesn't show as unregistered. Haven't tried converting anything, though. What does the expiry date mean?