Thanks for the reply. My guess is that the main motivation he trusted the code to you is that he is worried that by releasing the code, it will become polluted with bugs, bad ideas, and lose the vision and focus that has made it so powerful, flexible, and elegant. He trusts you to share his vision and knows you have the ability to at least make small changes and keep the website going.
But I really doubt the reason for not releasing the code has anything to do with protecting valuable IP -- ie algorithms that can be patented or secrets that could not be easily replicated from scratch. Altogether, it's a large, complex program, but if you look at any one piece, I'm sure it's composed of very simple functions.
Maybe he didn't consider the compromise approach I suggested. If you still have a channel open to him, can you ask if he would be willing to give you sole authority to commit changes to the project or bless other "experts" with that authority, but open the code on Source Forge (minus any commercial components), so that anyone can download and modify it?
I think that's the only way to really ensure this thing will survive. The proprietary components need to be replaced with open software so that it's not just limping along and accumulating bugs until they are beyond your ability to fix it.
Jason