I can assure you, the Banshee UrlToolkit rules work fine. For the Banshee PHP framework that is. The apache rewrite rules you mentioned look like this for Hiawatha:
RequestURI exists Return
Match .*\?(.*) Rewrite /index.php?$1
Match .* Rewrite /index.php
I've taken a quick look at this fat-free framework. I doesn't look like a clean and solid framework to me. I this really what you want? I advice you to take another look at Banshee. It's better structured and more secure than this fat-free thing.