Some other prominent Web Traffic Analyzers like to Zoomstats are:
Web Trends
Wusage
Hitbox
eXTReMe Tracking
But Zoomstats is under the GPL(GNU Public License) meaning it's completely free and Open Source. Therefore you can avoid the high prices of other Web Traffic Analyzers.
Portability
ZoomStats is a software for every usage. It will have to support every database known to the world right now. It is not a very hard thing to do: PHP supports quite a lot of databases today and, thanks to the Object Oriented Design, ZoomStats will be able to work with each one of them. Early versions will support MySQL, PostgreSQL, and Oracle.
Statistics
There are 3 ways to get the client's data:
PHP file
JavaScript code
Examining your web server's log
ZoomStats will support all three ways. It is possible because the statistics will actually be held within a database, and therefore the preferred collecting way can be independent from the application. At first ZoomStats will include the PHP and JavaScript method the Sever log files method will come out later.
Installation
The installation process is simple and currently documentation on it (if you encounter any problems) is being written, just in case. ZoomStats will have a feature that warns the user when a newer version is out.