Metagame consists of the off-screen simulation of events and interactions of NPCs and Zombies between themselves and their environment. The metagame becomes concrete when the simulated characters and events come "on-screen."
For example, the gunshots heard and the helicopter or airplanes passing overhead are metagame events. As of RC 2.9, however, the player can't find who fired the gun or where the helicopter or plane went. The dead will still follow the sounds, sometimes passing (or eating) the player, originating from somewhere off-screen.
In the future the metagame could involve complex interactive storylines, influenced by the environment, random events, NPCs, or the player. Most NPCs, however, would just be random survivors just trying to make their way. But certain NPCs would have storylines in which they make AI decisions and have scripts; the decisions and scripts would change depending on random chance or input from other NPCs, the environment, or even the player. For example, in the Kate and Baldspot story, the player could take the position of the raider. Presumably, the raider-player could threaten Kate, kill Bob (or do something else). In other words the player takes part in the storyline, becoming a participant in the script and thus changing the script and the NPCs, and finally the metagame.