[JDEV] Creating custom registration modules

[Per Eckerdal]

Hi jdev!
I want to make a chat client (using jabber), so far so good (I'm using
smack), but I want to integrate it into my website by changing the
user handling module so it checks if the user is registrated in my
site by calling a php script instead of these xml files and the same
when registrating a new user.. In other words, is it possible to create new 
registration modules in jabberd (or any other open source) server?
 /Pelle