I will check this out, Myspace has been updating their pages lately, so I'm not sure whether they changed the way that they display whether a user is online.
Just to give you some information:
The scripts SHOULD show when a user that has NOT disabled the option to appear online in the options is online. For example, if you have a friend who IS online and you can see the person in the "People Online Now" section in your Inbox, then the scripts will show that person as online if they have tried to hide the "Online Now" icon on their profile using some HTML or CSS.
The short answer: If the person has disabled the ability to display their online status in their options, then, no, the scripts will never display them as online.