Of course it supports multiplayer (That is if you have Comm or Pro). However, the question I think your refering to is if it will support large quantities of players and data, such as an MMORPG or a world-based chat (Which would require pro).

First things first, you'd need the Professional version.

There has been alot of arguments on the networking speed (or lagging) of large multiplayer games in 3DGS. However, those who sayed it could not be done have no evidence to support their claims. But those who say it can be done, have already done it AND showed us examples and/or demos.

So in short, if you have the pro version then yes, you can. But it will also require a lot of other info such as server speed, efficiency of database usage (for storing IP's, titles, names, entities, etc).