There are two ways to customise FFCRM, the first is to add your own custom fields and tags which can be done through the GUI, the second is to extend the code using Ruby on Rails. There are several people on the list who can help you for a fee.
What features are you looking for? If they are useful to us too, we may build them for free as we are doing some work on the code too.
Regards
Richard Stobart
Unboxed Consulting