1. Bring first 3 ingredients to a boil in a 3-qt. saucepan over high heat; boil, stirring occasionally, until sugar is dissolved (about 4 to 5 minutes). Reduce heat to medium, and cook 10 minutes or until mixture is reduced by half. Remove from heat, and stir in mint. Let stand 5 minutes.
2. Pour mixture through a fine wire-mesh strainer into a bowl, discarding mint. Scrape seeds from vanilla bean into bowl; whisk until blended. Reserve vanilla bean pod for garnish.
3. Cut 1 cantaloupe half into 10 thin wedges. Cut 2 thin wedges from remaining half of cantaloupe; reserve remaining cantaloupe for another use. Place cantaloupe, raspberries, orange sections, and honeydew in a 13- x 9-inch baking dish; pour warm syrup over fruit. Cover and chill 3 to 24 hours. Remove fruit from syrup using a slotted spoon. Arrange on a serving platter. Serve syrup with fruit. Garnish, if desired.
*1 Tbsp. vanilla extract may be substituted. Stir in with mint.
Note: Be sure to scrub cantaloupe rind with a vegetable brush before cutting into wedges.