Of course, there's a catch: This is still only a game trial. Although you'll be able to play with and against actual owners of the game online for as long as you want, the full-game trial has an artificial level cap. You'll only be able to advance your MAG character up to level 8, enough to unlock access to the game's signature 256-player mode. Any experience you earn after level 8 will go unrewarded until you purchase the full digital license for $30.
The trial's level cap means you won't be able to become a squad leader or change your faction either, but if you want to keep playing for free, simply put an artificial cap on your gameplay goals, too: Become the greatest level-8 soldier of all time.