The main difference between Owner and Proprietor is that the Owner is a legal term and Proprietor is a one who owns something.
Ownership is the state or fact of exclusive rights and control over property, which may be an object, land/real estate or intellectual property. Ownership involves multiple rights, collectively referred to as title, which may be separated and held by different parties.
The process and mechanics of ownership are fairly complex: one can gain, transfer, and lose ownership of property in a number of ways. To acquire property one can purchase it with money, trade it for other property, win it in a bet, receive it as a gift, inherit it, find it, receive it as damages, earn it by doing work or performing services, make it, or homestead it. One can transfer or lose ownership of property by selling it for money, exchanging it for other property, giving it as a gift, misplacing it, or having it stripped from one’s ownership through legal means such as eviction, foreclosure, seizure, or taking. Ownership is self-propagating in that the owner of any property will also own the economic benefits of that property.
One who owns something.
“The police recovered the stolen car and returned it to its owner.”
The captain of a ship.
A sole owner of an unincorporated business, also called a sole proprietor.
One of the owners of an unincorporated business, a partner.
One or more persons to whom a colonial territory is assigned, like a fief, including its administration.
“From 10 September 1621 till 12 June 1632, Sir William Alexander, styled Earl of Stirling and Viscount of Canada, was proprietor of the Scottish colony Nova Scotia.”
a person who owns something
“the proud owner of a huge Dalmatian”
the owner of a business, or a holder of property
“Chinese restaurant proprietors”
“by 1640 he was himself the proprietor of a three-hundred-acre tract”