It's been maintained:

The latest version of that document: http://udn.epicgames.com/Three/NetworkingOverview.html

How Unreal's content packaging relates to its networking architecture: http://udn.epicgames.com/Three/PackagesAndNetworking.html

How the game state is replicated: http://udn.epicgames.com/Three/GameStateReplication.html

How that packaged content is streamed to the client: http://udn.epicgames.com/Three/ContentStreaming.html

And somewhat older:

How events are simulated on the client: http://udn.epicgames.com/Two/SimulationReplication.html

How variables are replicated: http://udn.epicgames.com/Two/VariableReplication.html

How functions are replicated: http://udn.epicgames.com/Two/FunctionReplication.html