Maybe it has already been asked, but I did a quick search and can't seem to find it.
The title bar says "Option: Mobile", and I noticed the announcement post of the new version also mentions it.
A better than I can give you explanation here: http://dvdfab.com/dvd-fab-mobile.htm
Thanks, that explains it all!
Also now I think that if you get the mobile option it will cost you extra if you bought FAB after 5/8/08 but if you had FAB before that date it will still be free to you