What it means is that a one-time fee or subscription gives the right to use an image in a publication according to the terms agreed upon, with no license fees being paid for further use. (wiki)
As far as i understood your question, you have met this term in some "free download" template site... in other words, that means "free template (xhtml/html coded) and in the design of this template are used royalty free images (+/- professional images) and the template has already space for adsense (in other words, you just need to put your adsense code with the shape given there)"