There are dozens (possibly hundreds) of similar sites which either require an annual payment or accept a one-off payment for 'life-time membership'. In every case, all you get for your money is some software and possibly 'support'. (From what you've written, it sounds as if the site you've found is charging an annual licence fee to use their software). The payments never include copyright fees.
Please see my post here for further information about the legality of using such sites:
http://www.theanswerbank.co.uk/Law/Question353 035.html
(That post relates to a site which requires a one-off payment but everything written there will also apply to the site which you've found).
Chris