Ok, worked out how to do this without signing up for an account

Goto https://www1.gotomeeting.com/tgw/URL/g2w/joinwebinar?Portal=www.gotowebinar.com&Target=w/join_gotowebinar.tmpl

and type in the code from the "Register" URL which is 450730883 and your email address.

You should then be able to register for the webinar without going for the Free Trial.