Prepare a medium-hot grill or preheat the broiler. If using the broiler, line a rimmed baking sheet with aluminum foil.
Season the chicken with salt and pepper, to taste. Put the chicken on the grill or, if broiling, put it on the prepared baking sheet. Grill or broil, 4 inches from the heat, turning once, for 10 minutes per side.
Put 1/2 of the BBQ sauce in a small bowl, for drizzling and serving. Reserve.
Baste the chicken with the remaining sauce and grill or broil for 5 minutes more. Transfer the chicken to a serving platter, drizzle with some of the reserved sauce, and serve with lime wedges and the remaining reserved sauce.
In a small bowl, whisk together the ketchup, brown sugar, vinegar, onion, mustard, hot sauce, and black pepper. Stir in the scallions, lime zest, and lime juice. Can be covered and refrigerated for up to 1 week.
Yield: 2 cups