By default on Windows a new instance of your Revolution application will be launched each time the user double-clicks on your application or otherwise initiates a successive launch. As a developer you can override this behavior by intercepting the relaunch message (see Revolution docs). This lesson shows how the framework can handle this for you.
This feature is not available on OS X since an application can only have one instance running.
To limit your application to only one instance on Windows check the Single Instance checkbox. If this checkbox is checked and the the user attempts to launch your application while it is already running then the framework will intercept the relaunch message that is sent to the glxappLauncher stack (the stack used to build the standalone). After the framework determines if any files should be open the glxapp_relaunch and glxapp_openFiles messages will be sent to your application (see application stack script).