Not that most will be interested but recently the MMO The Saga of Ryzom opensourced its client and server code along with a toolkit to create and develop your own shard and MMO

Its written in C++ and more details can be found at http://dev.ryzom.com/projects/ryzom i've downloaded and managed to compile the server and client and grabbed the toolkit as that wouldn't compile for me lol, seems the maps are mad in 3ds max which is handy i have that, just thought i would share with the nerds

Cool. That's some step to take for an MMO.
I remember playing Ryzom back in the days! It wasn't half-bad!

I played it back in beta like 6 years back the concept was great especially with the Ryzom Ring but sadly looks like it was too ahead of its time and isn't as big as it could have been, of note http://dev.ryzom.com/wiki/ryzom/WindowsBinaries looks like it has compiled copies already for you but be warned, i downloaded 165MB of source and compiled a 2GB server so its not likely to be a small download for those with a cap, so far i have the DB's setup and they have some default data in, waiting on a fix for the now broken start_shard.bat issue which i could fix myself but that makes life difficult lol