Information about the selected files is of course available, and it's all documented in the manual.
StartupData is empty because at the moment there's no information that needs to be provided - it's a placeholder object for future development.
If you're holding off purchasing until we add exactly the scripting interface you feel you need you're probably wasting your time, because it's quite unlikely we would do that for an unregistered "evaluator".
If you'd bought the program four years ago and then requested improvements to the scripting interface there's every chance we would have implemented them already, if they weren't already possible. We do that a lot for our registered users, as a browse of the forum would quickly reveal.