FYI, to use that object, you'll also need /usr/local/lib/libfluidsynth.1.dylib. You can find out by running this in the Terminal:
hans@palatschinken:~/Desktop > otool -L fluid~.pd_darwin
/Users/hans/Desktop/fluid~.pd_darwin:
/usr/local/lib/libfluidsynth.1.dylib (compatibility version 2.0.0, current version 2.0.0)
/System/Library/Frameworks/vecLib.framework/Versions/A/vecLib (compatibility version 1.0.0, current version 150.0.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 71.1.1)