Married

This is a page consisting of evidence supporting that:

Steve Purcell's wedding toppers

screenshot of Sam & Max at the alter in the recap section of the first episode of the cartoon

Confirmation from Steve Purcell

While limited to Sam's imagination, this shows that Sam put thought into proposing to Max.

Valentines day drawing by Steve Purcell

Max referring to Sam as a first lady

Sam referring to Max as his copain. Although the word does have a meaning of buddy, the people of France almost never use the word for such and instead use pote. the word copain is very often used for boyfriend.