Open Server

How would you go about making open servers for MMORPG's or such? Has anyone made one before? Is it possible?

Open in what way? Source? If its that I wouldn't recommend it. If you're making an MMORPG then I suggest you read these,
http://www.devmaster.net/articles/mmorpg-postmortem/part1.php
http://www.devmaster.net/articles/mmorpg-postmortem/part2.php
http://www.devmaster.net/articles/mmorpg-postmortem/part3.php
http://www.devmaster.net/articles/mmorpg-postmortem/part4.php
http://www.devmaster.net/articles/mmorpg-postmortem/part5.php

Those are interesting but not what I meant. Sorry, I should have phrased my original post better.

Have you ever played the online game, Runescape? It has multiple worlds with a max limit of players per world. Anyone anywhere can connect, not just LAN. How would you make server's like that? they would have to work in the USA at least. I've never played World of Warcraft, but I bet it has a similiar setup.

I tried the one in the code archives but it only works locally.