Woops

osu.Desktop/Program.cs

@@ -26,7 +26,7 @@ namespace osu.Desktop
             {
                 host.ExceptionThrown += handleException;
 
-                if (false)
+                if (!host.IsPrimaryInstance)
                 {
                     var importer = new ArchiveImportIPCChannel(host);
                     // Restore the cwd so relative paths given at the command line work correctly

osu.Game/OsuGame.cs

@@ -150,7 +150,7 @@ namespace osu.Game
 
             ScoreManager.ItemAdded += (score, _, silent) => Schedule(() => LoadScore(score, silent));
 
-            if (false)
+            if (!Host.IsPrimaryInstance)
             {
                 Logger.Log(@"osu! does not support multiple running instances.", LoggingTarget.Runtime, LogLevel.Error);
                 Environment.Exit(0);