On my website users can go into their profile and
put their adsense sponsors on there. The do this by adding their
publishid and ad code in their profile setup. Once this is done the
sponsors page shows up in the users' profile page.

The problems is this. Users who don't own a website can apply for an
adsense account unless they do own a website. So how can a user sign
up without a website? Can the user put as their website www.website.com/username
which is their profile or put www.website.com?

So what I'm asking is, can a user get an adsense account without having to own a website? Or can the user just use my website and their profile address as their website address?