I'm not definate, but I would definatly imagine there would be...I'll have a look around the site to see if I can find anything, but otherwise try contacting Jack (jack@gossamer-threads.com), I think he is the one to ask regarding this kind of thing.
Just to be clear, the official answer is one license covers one installation on one domain only (like most software, i.e. you can't install Office on every computer in your company with one license).