Unfortunately, there is a little problem - the GNUstep libraries are usually not registered with ldconfig; so, before starting Apache, you need to make the libraries available. Simply typing:
. /usr/local/GNUstep/System/Makefiles/GNUstep.sh . /usr/local/GNUstep/System/Makefiles/ld_lib_path.shbefore starting Apache should fix the problem. If you want, you can just put these two lines inside your shell configuration script.
You should be able now to use the module. For example, to serve the files with extension .nicola using the trivial Apache module above, you just need to add the line
AddHandler my-handler .nicola