The StartWindowTitle is a required parameter for WebStart launcher. The reason is that Marathon needs to identify the application window as opposed to the webstart launch windows.
You can use a regex for startWindowTitle that can capture both the window titles and the use getTitle in the test script to conditionally evaluate the code. If the startWindowTitle starts with a '/' it is considered as a Java regex.
HTH.
Kind Regards,
KD
BTW, we released a commercial version of Marathon for Eclipse. You might be interested in that :)