I would like to recommend S2U - a free of charge tool for porting S60 application to UIQ. The porting is simple, fast its results are excellent. The porting process is comprised of 3 steps:
STEP 1: Automatic Series 60 Project File Conversion
STEP 2: Building the project in the UIQ environment
STEP 3 (May be required in some cases): Minimal manual original source code adjustments.
The tool is from Peroon R&D Ltd. and can be downloaded from http://www.peroon.co.il/s2u.html. In case any problem occur, Peroon's free of charge support is very efficient.
Does this mean any S60 app will run on UIQ?
Dare we speculate something like TomTom Mobile? 🙄
what about n-gage games? :P
S2U provides implementation of UI-related S60 APIs on UIQ. That means that:
1) application has to be rebuilt on UIQ from its C++ sources
2) non-UI incompatibilities require manual intervention to the C++ code
3) while standard S60 controls will behave as standard UIQ controls, the hard-coded screen coordinates, etc. will not be "translated" automatically, and thus will require manual corrections.
Nevertheless, S2U makes the porting much easier and faster, and - after the porting is done - you will have to maintain only 1 source code for both S60 and UIQ platforms.
n-Gage games? Why not? S2U package even includes a game as an example. It is also a good example how to cope with my note #3 (about screen coords, etc.)