Do you have to be a resident of NS or Canada to write for a provincial board?

Nope! There are probably some different fees you have to deal with, but there isn't a resident restriction: alot of nurses at my hospital are from other provinces, and while some take 'reciprocal' consideration (ie: the license from province 'a' can be basis enough for issuing a license in NS) other folks have had to write the exam.

If you google 'College of Registered Nurses of Nova Scotia' (CRNNS) you should be able to find the info there :)