In medium saucepan, bring 2 1/2 cups water and lentils to a boil over high heat. Reduce heat; simmer 15 to 20 minutes or until lentils are tender; drain. Rinse with cold water; drain well. Cool 5 minutes.
In medium bowl, combine cooked lentils and all remaining ingredients except oil and mustard seed; mix well.
Heat oil in small skillet over medium heat until hot. Add mustard seed; cover and cook about 3 minutes or until seed pops. Remove from heat. Add seed to salad; stir to combine.