edited the LobbyLogic to include a spectator toggle in the server admin dropdown.

OpenRA.Game/Network/Session.cs

@@ -127,6 +127,7 @@ namespace OpenRA.Network
 			public int RandomSeed = 0;
 			public bool FragileAlliances = false; // Allow diplomatic stance changes after game start.
 			public bool AllowCheats = false;
+			public bool AllowSpectate = true;
 			public bool Dedicated;
 			public string Difficulty;
 			public bool Crates = true;

OpenRA.Game/Server/Server.cs

@@ -276,6 +276,13 @@ namespace OpenRA.Server
 					IsAdmin = !LobbyInfo.Clients.Any(c1 => c1.IsAdmin)
 				};
 
+				if (client.IsObserver && !LobbyInfo.GlobalSettings.AllowSpectate)
+				{
+					SendOrderTo(newConn, "ServerError", "The game is full");
+					DropClient(newConn);
+					return;
+				}
+
 				if (client.Slot != null)
 					SyncClientToPlayerReference(client, Map.Players[client.Slot]);
 				else
@@ -317,7 +324,7 @@ namespace OpenRA.Server
 				LobbyInfo.Clients.Add(client);
 
 				Log.Write("server", "Client {0}: Accepted connection from {1}.",
-				          newConn.PlayerIndex, newConn.socket.RemoteEndPoint);
+						  newConn.PlayerIndex, newConn.socket.RemoteEndPoint);
 
 				foreach (var t in serverTraits.WithInterface<IClientJoined>())
 					t.ClientJoined(this, newConn);