IGN: "How do you make money from a six year old game? According to DICE and Easy Studios, the studio behind Battlefield Heroes did for Battlefield Play4Free, it's release it for free with a bunch of optional microtransactions! Battlefield Play4Free is essentially a rereleasing of a handful of the maps from Battlefield 2, with a leveling system and weapon shop that lets you upgrade and customize a persistent character.
Right now there are two big problems with Play4Free. The first one is the way characters are handled. If you plan to never pay a cent, you are locked into only having two playable soldiers. That means that if you make a Medic and an Assault fighter, then you can't play a Scout or an Engineer. You currently can't delete your characters -- you can only buy more character slots. It doesn't seem like much of an issue until you get into a match where, by sheer random luck, 90% of your team is the same class."