The free 'Agents of Change' DLC for Brink will arrive on August 3 on Xbox Live and Steam and the following day on PSN.
As long as you download Agents of Change during the first two weeks it becomes available you'll be able to play it for free forever.
Bethesda's also put out a bunch of new DLC screenshots, which you can see at the bottom of the page.
Win Labs as both factions in Campaign Mode
Win Founders' Tower as both factions in Campaign Mode
A Burning Thing:
Kill an enemy with a Napalm Grenade
Kill an enemy with a Pyro Mine
Kill an enemy with a UAV
Have a Field Regen Unit buff more than 3 players simultaneously
Reach Level 24