Porting from BlackBerry to Series 40 by inari explains what needs to be taken into account when porting BlackBerry apps to Series 40.

BlackBerry devices (up to BlackBerry OS 7.1) and Series 40 devices share the same development platform – Java ME. This makes porting from BlackBerry to Series 40 quite straightforward and transparent, especially when compared to other mobile platforms. Many generic Java ME libraries can be reused on both platforms “as is”.