I know what you mean about the connecting to the internet. My boss says they've tried to reduce it so that if you disable the check(s) in the menu system, it shouldn't try to connect at all.

Make sure the two checkboxes under Options/Settings General Tab that are for Permissions are unchecked. Then, disable CD lookup (under CD Lookup/Connectivity). With these unchecked, the only other ways MMJB should try to connect is if you initiate the connection. This can be done in many ways, such as opening the Guide, Radio, or Now Playing windows, clicking on the Radio tab (in the playlist), using SuperTagger, etc.

But, for basic playback, library organization, etc., it shouldn't try to connect. Unfortunately, most of the cool features require you be connected to the internet.