The User's Manual contains a description of the entire UI and some rendering guidelines.
Video tutorials created by Chinny from Softimage. They give a nice overview of how the plug-in integrates in Softimage and show some of the original features of 3Delight for Softimage.
All release notes since the release of version 2.0 in January 2011.
This guide explains how to obtain and install the license key and start the license server. Note that this is not necessary for the free version.