The installer is on this page as well as links to avsim to download airline packageshttp://www.world-of-ai.com/allpackages.php
I am not sure why you got the forbidden message it is a legit site.
When you download and unzip installer keep the installer where you plan to use it with all folders as unzipped. Right click on WOAI Installer.exe and run as administrator or they will not install traffic and all your default traffic will not show either with Windows 7 or 8. Install all liveries you want to add and happy flying.
Direct WOAI Installer.exe to the zip files of liveries and it will take care of it for you so don't unzip liveries.
The file as unzipped and a picture at Phoenix Skyharbor hub of Southwest and US Airways