To sum it all up, the answer to the question Does PokerStars allow HUD? is, yes.
Here's why you should use Poker Copilot as your PokerStars HUD: Poker Copilot has worked with PokerStars since 2008. We're on their list of officially approved software. Poker Copilot supports scheduled tournaments, ring games, "Sit & Go" tournaments, "Spin & Go" tournaments, and Zoom Poker (Zoom for Mac only).