I just took a look at the PHP-Nuke 6.0 code & documentation, although I haven’t actually tried it yet. I really like what they did in this version – all of the configuration stuff that used to be in config.php has been moved to a database table. The only thing in config.php now are pointers to the SQL database, where it gets the rest of the configuration information.
This is a huge improvement, since config.php was always a pain to maintain. If I wanted to be able to change it from the admin screen, I had to keep that file writable. Plus I would often change it on the server and forget to back up a copy to my local machine (for the rest of the site, I always make the changes locally and upload them to the server).