UltraStar Deluxe is a clone of UltraStar, although it features a more intelligible interface and more attractive game modes.
Now you can play with up to six singers in UltraStar Deluxe, although you'll need a microphone for everyone.
Party game mode is the same you can play in SingStar. Your goal is to win throughout the different tests and games purposed by the game: duel, blind sing, up to 5000, etc.
Yes, we could say it is Singstar for Mac, Ultrastar Deluxe is more than a karaoke, give it a try, it's free.