Usually all Content Providers will allow you to use the licenced photos on a specific amount of urls, doesn't matter if this are free or pay sites.
We, for example, allow you to use the photos on up to 9 domains with the standard licence. The difference to others is, you can also change the domains for which the content was licenced before. Therefor we do not care on which domains you will use the content, as long as it will not be used on more than 9 domains and you are updating the licenced domains for the content within your personal admin area at
http://www.skan-media.net