And if I want to use an MDI then what are they going to do about it?
Quite simply, if you want to do something that the system doesn't support natively, you should be prepared to code it yourself.
We could argue until we are blue in the face about violins, MDI windows and a coders right to design their own interface, but MaxGUI, unlike wxWidgets, isn't (and doesn't pretend to be) a complete GUI toolkit for advanced programs. If you want to do anything out of the ordinary, you should probably look elsewhere.
The Mac implementation of wxWidgets allows the use of MDI, except it works in a way where your Child windows are just child windows, not embedded ones...
I'm not sure how I've managed to annoy so many people, but this is effectively what I've been saying. MDI WINDOWS (IN THE SENSE OF A WINDOW *WITHIN* A WINDOW) AREN'T SUPPORTED NATIVELY ACROSS ALL PLATFORMS.. MaxGUI can have child windows, but we don't try to pretend we support MDI when it simply doesn't on other platforms. Native MDI isn't cross platform.