It really is a poorly setup installer.
They have the .app sitting in the root of the pkg, but they are shoving growl and macfuse in the postinstall and postflight respectively. And then they are shoving Application Support in through traditional pkg means.
If you were to copy the pkg to the desktop and rip out the growl and macfuse folders From Contents/Resources, you won't get those. But, I don't know if ZumoCast relies on macfuse. If it does, you would need it.