Elysium is a older game maker that recently has made a big comeback
as an easy, but completely customizable game maker.
It uses Visual Basic 6 coding, along with simple BMP graphics
files and tilesets.
It is a 2D gamemaker, but good 2D.
A standard game would be about 100-200MBs big with it (client)
And the server 20-40MBs.
Although one of the main catches is that you need a good host
to run this. It uses up bandwidth like crazy
(Unless you convert it to IOCP instead of its native packet system)
There are actually several different companies/organizations creating
engines out of it here are the ones I know of:
Elysium (Well known for Diamond): http://splamm.com/elysium/
Eclipse (This version isn't opensource, and doesn't have good rep with other makers): www.touchofdeathproductions.com/
Elysium Blue (Converge with Greentail): http://www.thefmp.com/elysium/
And for those who are wondering, Elysium's definition is: "the abode of the blessed after death in classical mythology"
or: "paradise"

