Bring water to a boil in a medium saucepan. Add shrimp; cook 3 minutes. Drain shrimp in a colander over a bowl, reserving cooking liquid. Add couscous to reserved cooking liquid. Cover and let stand 5 minutes. Fluff with a fork.
Combine couscous, shrimp, tomatoes, green onions, and basil in a large bowl. Combine broth, lemon juice, oil, salt, and pepper. Pour dressing over salad; toss gently to coat. Sprinkle with cheese.