The server Windows XP/Windows Server 2003 or above with support for the expected user load (see cost to host).
The server software makes use of Torque Dedicated servers and it's networking protocol to host players in each zone. Zones are controlled by python logic which brings all of this together. Clients connect using the Torque front 3D engine (TGE) and all data is stored in a SQLite database. Consistency between clients are controlled by python which acts as a mediator between the game world, the zones and the clients. Additionally, our web infrastructure will connect into our SQL data to provide server stats and account tools on the website. This is probably best done with a push mechanism rather than direct access. Security needs to be discussed before this is implemented
The Server software operates on Windows environments and can (and is) split across several zones which operate in a mixed configuration. Zones are loaded on launch and can be linked together via Portals which operate as gateways between zones. These portals do not have to be physical. They can be ravines or tunnels or simply a line across the terrain that when crossed sends you to the southern end of the zone.
Cost to host
It will cost approximately 30c in bandwidth and processing power to host every user. Micro-transactions are probably the most efficient way to break even.