Hi,
for some experience programmer that want make a mmog with unity or any other game engine 
Darkstar is a project from Sun and NCSoft use it for internal prototyping at the moment.
We use it for half year now and are really impressed from darkstar. it isnt a complete out of the box game dev kit for mmo(g)'s. But it handle the most problems with mmo(g)'s (network/sync data).
https://games-darkstar.dev.java.net/index.html
Official Description:
‘Project Darkstar is the game industry?s first open source, enterprise grade, highly scalable, online game server. From Massively Multiplayer Online Games to Casual Games, Project Darkstar can accommodate the varying needs of the online game developer through a single solution. Providing easy to use, simple API interfaces, Project Darkstar will have you up and running in a fraction of the time that it used to take in standing up online game solutions.’