You can configure it using django-hosts, so you wouldn't have to mess with web server itself ad do everything in django. If you will give me some concrete examples, I could help you with configuring this app.
Edit
I am not sure how to tackle that problem, since I can not think of any way you can get any information from arti.com if you don't have access to the actual server arti.com is pointing to. However, I can suggest not using referer=Arti
style patterns in urls, use something like that instead: url(r'^invite/(?P<referer>[\w-]+)/', ...)
this way it won't be stripped out.
Also with django-hosts you can setup urls with subdomains. Basically you could setup urls to be arti.mysite.com
, then in view you would have access to subdomain part, arti
in this example, which I believe can solve part of your problem.