Place sausage and 1/2 cup water in a large (12-inch) skillet. Cover and bring to a simmer. Steam until sausage loses its raw color throughout, about 8 minutes. Drain and set aside.
In a medium bowl, mix oil, cumin, curry powder, garlic powder, ginger, salt and cayenne. Scrape half the spice mixture into another medium bowl. Add lamb chops to one bowl; toss to coat well. Stir yogurt and vinegar into other bowl; add chicken legs and toss to coat well. Set both aside to marinate.
About 30 minutes before serving, fully preheat gas grill (10 to 15 minutes with all burners on high). Use a wire brush to clean grill rack, then use tongs to wipe an oil-soaked rag over rack. Close lid and return grill to temperature. Make sure to have water close by to extinguish any flare-ups.
Staggering meat additions so they all get done about the same time, place chicken on grill; close lid and grill-roast for a total of 20 minutes - 8 minutes on the first side, 8 minutes on the second side and 4 minutes longer, turning as needed toward the end to ensure doneness. Add lamb; grill-roast for a total of 8 minutes - 4 minutes on the first side and 4 minutes on the second side. Add sausage and grill-roast for a total of 4 minutes - 2 minutes on the first side and 2 minutes on the second side.
Arrange on a large platter and serve warm with couscous.