In a 1 quart saucepan, heat water to a boil. Add salt and couscous. Cover, reduce to a simmer and cook stirring occasionally for 8 to 10 minutes. Remove from heat and cool slightly. In a small bowl, combine the dressing ingredients and mix well. In a large bowl, gently toss the cooked couscous, beans, cucumbers and green onions. Pour the dressing over couscous mixture, gently toss to coat. Add tomatoes and gently toss. Serve warm or cold.