Taking over a license and moving ISPs?

I've just taken over a project that involves moving the site from the developer's servers to our ISP and moving it from one domain to another. It looks like that would be no problem if I had bought the original license, but our developer did that and then billed us for it. Is there a way for me to take over the license so that I can make it work for our production site?

the best way to go about this is to get the login information from the developer.

Thanks. The developer has sent in a request for this.