You are correct. If it's not posted. It's legal to CC or OC there, however, if asked to leave you must do so or face trespassing. I OC'd in a bar in Portland from 10pm to 1am one night and nothing was said to me. I don't even think the staff noticed.
Some people also misread this statement to apply to all businesses. But it says a "licensed establishment" which in Maine means an establishment with a license to serve liquor for on premises consumption, ie. bar.