Shortly before the release of Driver: San Francisco, Ubisoft announced that it was initiating a new profit-security system called Uplay Passport -- a code-based "online pass" included with each new retail copy of the game that was required in order to activate the online multi-player side of the game. The logic being that players who bought the game used were depriving the company of income for the title, and if they wanted to play the online side of the game, they would have to purchase a Uplay Passport for the game from either the LIVE Marketplace or PSN (depending upon the version of the game that they bought used) for $9.99 -- thus ensuring that Ubisoft obtained at least some profits from the resale of their games.
Ironically a snafu in the packaging process for Driver resulted in a large number of retail copies shipping without the code card being included in the sealed package, with gamers reacting badly to the fact that they could not play the online side of the game and, with some vocally suggesting that Ubisoft did it in purpose to gain an extra $10 from them.
It was then discovered that in addition to many copies not having the card inserted, copies that did have the card had codes that were misprinted, and did not unlock the Passport.
Ubisoft's reaction to the snafu was to make the Uplay Passport free for the game, and altering the 3-Day standard trial selection in-game to a full free Passport as well, so the "test" for this new standard was not a success.
The inclusion in Revelations will hopefully be a much smoother process, but if you purchased your copy used -- or rented it -- you will have to either be satisfied with a 3-day trial play for free, or pay the $9.99 for a full license.
When you play the game for the first time it will check the status of the Passport for your Gamer Tag -- and if it does not include a license, it will prompt you to Activate your Passport, and include the option to purchase a Passport or opt for the 3-Day Free Trial.