Ok, I promised this like 8 weeks ago and I apologize for being so late
Download the 3 things on that page and you should be good to go for adding CAS authentication to ILLiad and Aeon.
I will be loading these up to SourceForge once I find my account info and will follow up again. Feel free to ask questions and don't slaughter me, that is the first pass at instruction, I hope I didn't leave out anything major.
It is also important that I give credit where credit is due. All of the work documented is based on the implementation of CAS for Aeon by Jay Terray who works here at Yale in the Beinecke Library.
I will also mention that while the instructions are for CAS, you could easily adopt this authentication method to ILLiad to use any sort of external authentication/authorization system you have.
Questions, just ask.
Manager, Digital Library & Programming Services
Yale University Library