To clean live mussels, scrub under cold running water. Remove beards. In an 8-quart Dutch oven combine 4 quarts of the cold water and 1/3 cup of the 1 cup salt; add mussels. Soak for 15 minutes; drain and rinse. Discard water. Repeat soaking, draining, and rinsing twice more.
In a 15x11x3-inch disposable foil pan combine tomatoes, wine, oil, garlic, crushed red pepper, the 1/2 teaspoon salt, the oregano, and lemon.
For a charcoal or gas grill, place foil pan and sausage pieces on the rack of a covered grill directly over medium heat. Grill for 3 to 4 minutes or until sausage is brown and heated through, turning sausage and stirring tomato mixture once halfway through grilling. Remove sausage from grill; set aside.
Stir mussels into tomato mixture in pan. Cover and grill for 6 to 7 minutes or until shells open. Discard any that do not open. Stir in sausage pieces and kale. Cover and grill for 2 minutes more.