Maine addresses knives in two ways: Threatening Display and Concealment.
It is illegal to brandish in a threatening manner a "bowie knife, dirk, stiletto or other dangerous or deadly weapon usually employed in the attack on or defense of a person." (Part A)
It is also illegal to conceal the aforementioned. (Part B)
Open belt carry is neither threatening nor concealment. And a "Knives used to hunt, fish or trap as defined in Title 12, section 10001" are exempt from concealment restrictions.
The RAT Izula could be considered a bowie, but more likely it could be be argued effectively as a hunting/fishing knife due to it's small size and utilitarian appearance.
Ok I couldn't resist bringing this up. Fishing in Maine is defined as:
23. Fish, the verb. To "fish" means to take, catch, kill, molest or destroy fish or to attempt to take, catch, kill, molest or destroy fish.