Remove giblets and neck from duckling; reserve for other uses. Rinse duckling thoroughly with cold water, and pat dry. Prick fatty areas of duckling with a fork at intervals. (Do not prick breast.) Lift wingtips up and over back,, tucking under the duckling securely. Combine 1/2 teaspoon salt and 1/4 teaspoon pepper; sprinkle over surface and in cavity of duckling. Close cavity with skewers, and truss. Fold neck skin under, and place duckling, breast side up, on a rack in a shallow roasting pan. Bake, uncovered, at 350° for 1 3/4 hours or until drumsticks and thighs are easy to move. Transfer duckling to a serving platter, and keep warm.
Skim fat from pan drippings. Discard fat, and set pan drippings aside.
Combine sugar and vinegar in a heavy skillet; bring to a boil. Reduce heat to medium high. Cook, stirring constantly, 5 minutes or until sugar is caramelized. Add grated rind, orange juice, and curaçao; simmer, stirring constantly, until sugar is dissolved. Add pan drippings; bring to a boil, and cook 1 to 2 minutes, stirring constantly. Stir in lemon juice and orange rind strips, if desired. Pour sauce over duckling. Garnish with orange slices and parsley, if desired.