It's pretty simple, tell me this:
Run the application OUTSIDE RR, then bring up the dialog,
1-can you still click/use the window behind it ?
2-when you click the window bellow (The main window), does the dialog disappear behind it ?
If the answer to 1 is YES, then the dialog is NOT modal. If the answer to 2 is YES, then the dialog is not parented by the main window (despite of what he may tell you). This really is a simple change, regardless of the language used, question is if you'll find somebody to apply it. Yes, all windows have a parent, even if it's the desktop window (owned by windows), but this is no requirement -- it's only a choice of the programmer.
On another note, he may not HAVE to use setparent, as he should probably be providing the window handle for the parent window when creating the dialog.