Hi Folks. I'm an old timer here, so I know some might jump and say that isn't Darkbasic? But it is a powerful framework that is free and with some work could easily be your server for your multi-player games.
This is a 500meg download, check out the sneak peak so you can at least see what it looks like before deciding to download a monster and then wrestle yet another installation program...
By the way, there is over 130,000 lines of source code in this one from yours truly. (Proud of that bit)
So... released yesterday... The Jegas Application Server, 10 years in the making, released open sourced GPL3:
http://www.jegas.com/index.php/offered-products/download-jas