This is only source code, and there are dependencies you have to build as well. The easiest way to install this would be through the MacPorts package manager, although right now, the latest version it has is 3.3.
Extremely comprehensive reporting, and very useful stats about network traffic. Impressive.
It would be helpful to have some more detailed instructions on how to set up some of the features, but trial and error can get results anyway, and it is free.