@doctorj
I already gave you a link to the mailing list, try it please.
A quote from a recent post by the author there (January 30):
> I an a registered user of Make-CD and wonder where I find my "reg code"
It should be on the postcard that you got back when registering or - if
you bought MakeCD more recently - it was already included in the package
that you got.
If you cannot find either, please send me the details about your copy
including the preliminary key and serial number to me privately and
I'll send you a replacement.