I've deployed WebAuth on Mac OS X 10.5.2 Server a couple times now on dev servers. It involves compiling Apache from source. Blech. Now your server will have three Apaches on it—a whole band, if you will.
I'm writing up an article now on how to do some of this. There are Mac OS X-specific considerations that a systems admin needs to take into account, which might not be obvious.
It would be wonderful to read about how you did this, when your article is ready. Thanks....