NanoFL 3.0.5 currently only features a .exe binary for windows. The program itself is wrapped with XULRunner from Mozilla and that makes it easy to run natively on Mac OS X.
If you have a current Firefox there is no need to install XULRunner(which anyway seems deprecated). You can execute XULRunner apps with -app switch. Use Wine to install the game and then copy the installation folder somewhere accessible. In the terminal you then execute the following to start NanoFL.
/Applications/Firefox.app/Contents/MacOS/firefox -app
/Users/headchant/Downloads/nanofl/application.ini
or more generic
/Applications/Firefox.app/Contents/MacOS/firefox -app /path/to/your/application.ini
Use no line breaks and edit the path to your installation of NanoFL.
This should start NanoFL inside a Firefox instance with almost all features as the windows version. Have fun! 