Thank you all. I decided there wasn't really a good choice for what I wanted to do so I ended up purchasing a Unity3d Pro license (
www.unity3d.com/unity) and am working with some old friends from Riot Games and Turbine to make our own little ORPG. It won't be nearly as big as NWN but we also don't have to worry about money since we're only doing it for us.
Here's our design goal, if anyone is curious.
Goal: To create a persistent world in which players can log on, roleplay with each other, and play the game without a DM overlooking them. However, special events can be run by a DM including large scale events such as invasions, medium sized events such as a rare mob spawning in a dungeon, or personal quests for individuals who get unique skills, items, spells, or something similar. The idea is for the world to have a maximum of 30-35 players at any one time, allowing for personalized content for each player while still maintaining a sense of community. Essentially, medium-scale, online D&D that doesn't require a DM at all times. Please remember this isn’t for commercial use.