MapleGlobal
MapleGlobal is the main gateway used by the vast majority of English-speaking players. It is available to all countries without a localized version of the game (ie. South Korea, Japan, China, Taiwan, Thailand, Singapore and Malaysia).
MapleStory Global is also known as GlobalMS, GMS, and OMS (Official MapleStory).
The 5 available worlds (also referred to as servers) are Scania, Bera, Broa, Windia and Khaini. These names are taken from MapleStory Korea. The BETA world, Tespia, was removed several months ago.
MapleStory Global is currently at ver. 0.21, and is run by Wizet and NXGames. Ludibrium is now out, having been released approximately one month ago. You can get to Ludibrium by riding the flying train, accessible through Orbis Station.