This project seems mostly dead... which is a damn shame cause its the best out there and I'd love to hop on board.
Regardless I'd like to post bug I've found, and I'm really surprised no one has posted it yet as it was a BIG hurdle for me.

I tried every version of DDWRT available for the WRT54GL and finally found a strange issue with chillispot not properly configuring the DNS server.

The symptoms were:
Re-direction would intermittently work. Sometimes it would work for a few hours. Sometimes it would only resolve the first uamallowed (ie. paypal.com but not paypalobjects.com). And sometimes redirection wouldnt work at all unless the original address specified was numeric (ie. 207.34.23.43 instead of google.com). Rebooting the router / enabling and disabling chillispot would randomly, temporarily, fix this issue.

The fix:
telnet into the router and manually edit the /etc/resolv.conf file to use the required DNS server. Mine was set to the default 192.168.1.1 which isnt even the same subnet as the chilli DHCP, so it could not use the static WAN addresses as one would hope. Changing this value to the ISP's external DNS resolved all issues with the server not starting, improper forwarding, and slow/intermittent uamallowed resolve.

Very strange issue. Hope this helps someone.

"chillispot[11283]: redir.c: 524: UAM port already in use. Waiting for retry." simply means chilli is already running. If you were to do a killall chilli before this command you would receive different results ie. you cant start chilli in debug mode because its already running (not that chilli's debug ever offers any useful info anyways).

And I would have to agree with Ilrl. Chilli has very little to do with logins. It simply forwards your information to the radius server and waits for the go ahead message. The radius configuration can be rather complicated. Seeing as your post is most likely dead I'm not going to spend time finding a chilli radius configuration guide on the web. Regardless, the configuration supplied with the webserver/radius debian install package should work well enough. Most likely, you just need to specifically edit the clients.conf config file to allow access to your AP's specific WAN address.