Spicy Orange Glaze: Place all ingredients in a medium saucepan and bring to a boil on the grill. Cook until reduced to 1 cup. Set 1/4 cup aside.
Chicken: Whisk together the oil, garlic and rosemary in a large baking dish. Add the chicken and turn to coat. Cover and marinate in the refrigerator for at least 4 hours or overnight. Preheat grill to medium-high. Remove chicken from marinade and season with salt and pepper to taste. Grill skin side-down until golden brown, about 4 to 5 minutes. Turn over and continue grilling for 6 to 7 minutes until cooked through, turning and basting with the Spicy Orange Glaze every 2 minutes. Remove from the grill, place on a platter and brush with the reserved Spicy Orange Glaze. Serve with the Orange-Pineapple Relish on the side.
Orange-Pineapple Relish: Combine all ingredients in a bowl and season with salt and pepper.