Heat grill to medium. Season the ribs with 1 teaspoon salt and ½ teaspoon pepper. In a small bowl, combine the Worcestershire, mustard, and brown sugar.
Place the ribs on grill, cover, and cook 20 to 25 minutes, turning often, until cooked through and tender. Baste with sauce during the last 5 minutes.
In a large bowl, whisk together the sour cream, horseradish, vinegar, ½ teaspoon salt, and ¼ teaspoon pepper. Add the cabbage, apples, and scallions and toss.
Cut the ribs apart, divide among plates, and serve with the slaw.