The client application is intended to be runned at logon/logoff to register session start/stop events thru the web service. The easiest way to accomplish that is to use GPO (group policy object) and add user logon/logoff calls to the client application (see -i and -o option).
The package also contains a Windows service (whosond.exe) that listens for WTS logon/logoff events. As running the service don't require special setup, its might be a better option for non-domain deployment.
The application is written in C# and you need to install .NET 3.5 as its runtime.