On eight 6-inch or four 10-inch skewers alternately thread the cantaloupe, honeydew melon, strawberries, pineapple, and bananas. Place kabobs in a glass baking dish. Combine orange juice and lime juice; pour evenly over kabobs. Cover; chill kabobs for 30 to 60 minutes, turning occasionally.
Meanwhile, for dip, in a small bowl stir together the yogurt and orange juice concentrate. Cover and chill until ready to serve.
To serve, arrange the kabobs on a serving platter; discard juice mixture. If desired, sprinkle nutmeg or cinnamon over dip. Serve dip with kabobs. Makes 8 servings.