The Assault Wing source code has been published on GitHub under the Microsoft Public License.
Check out
https://github.com/vvnurmi/assaultwing. If you're interested in tweaking something or developing the game further, by all means go have a stab at it :-)
Also, the public game server "AW Server 1"
will go offline on 2013-03-27. The server cost us money and there weren't many players to be served. The matchmaking server and the website
will stay online, however. It will be possible to play the game over the internet also in the future. One of the players will have to start a server that the others can then join. This requires that the server's traffic is not blocked by any firewall. Playing in a LAN should work without problems like before.