Drain juice from pineapple into small saucepan. Stir in pine-orange banana juice and cornstarch, blend until smooth. Bring mixture to a boil over medium high heat, cook for 3 minutes, stirring constantly. Turn heat off and carefully move saucepan to a cool burner. Combine pineapple, banana, orange, and grapes in a mixing bowl. When mixture cools to room temperature, about 15 minutes, stir in fruit. Spoon over pancakes. Topping can be used over frozen yogurt or waffles. Keep unused sauce refrigerated in an airtight container. Stays fresh for about 2 days. Heat before serving.