The free application is a GUI for the hidden VPN server in Mac OSX client OS. The application will configure and start/stop the L2TP & PPTP VPN server hiding in your Mac. All files necessary to do this are already part of the OS... so no Apple files are needed nor distributed by this application. This application is not intended for large scale enterprise use. It is rather intended for common folks that wish to establish a VPN connection to their home network via their personal Mac.
At the moment you can only create a single user/password/secret combination. This user/password is not one of the existing user defined on your Mac but rather a dedicated user/password dedicated for the VPN use.
Given that you properly configure you internet router to allow L2TP and/or PPTP across to your Mac you should be able to connect to your home network via your Mac running "VPN Activator".
If you expect to see your Bonjour shared resources to magically appear on the VPN connected device you will be disappointed. Apple's implementation of Bonjour does not work across a VPN. There are some ways of working around the limitation but none that can cleanly be packaged. So for now you will have to manually map network and printers shared on your home network.
This is not a limitation of VPN Activator but rather an Apple's implementation limitation of the Bonjour protocol.