You don't need a uPlay Passport to play online, but not having one limits your ability to unlock abilities and character accessories. I don't have a passport since I received the game used and I honestly wouldn't shell out the money for one.
eBay Link
This is a brand-new, unopened Fallout 3 Game of the Year edition for Playstation 3. I am willing to ship within the US only. Starting bid was $9.99 and currently only at $12.00! Only a few days left!