The application can be started via de commandline. Run as root: /usr/sbin/hiawatha and turn browser to: http://localhost/ The website can be found in /var/www
Remember that a webserver is a daemon that runs in the background, it's a server application. It's not a desktop application that gives you a point and click interface. To check if it's running, use the commandline tool 'ps'.
Unfortunately, MacOS X doesn't support uninstalling PKG files. Once installed, you have to uninstall manually. To do this, remove the following files:
Making a better MacOS X package is still on my ToDo list. Sorry for the inconvenience.
(on the other hand, why would you wanna uninstall such a great piece of software
and it's only about 100kb in size)