Here is the booklet - it specifically talks about residents and non-residents. It describes a traditional definition of Resident, but does not apply any definition to "Non-Resident". That in itself is curious, as they don't clarify it as "non-resident alien", or anything like that.
A quick read, what do you think:
http://maine.gov/dps/msp/licenses/do...%20Booklet.pdf
Edit: The form was changed in June 2013... hmm...