Combine the marmalade, vinegar, olive oil, and sage in a small saucepan. Cook over low heat for 2 minutes until smooth. Stir in the chives, then remove 1/3 of the sauce to serve with the chicken later on.
Season the chicken pieces with garlic salt and pepper. Grill for about 15 minutes on each side, then brush with glaze. Continue cooking until done, 20 to 30 minutes, turning occasionally, and brushing with additional glaze. Serve with reserved marmalade glaze.