To quote from the Kitely Services webpage:
So, for example, you can use KC instead of USD to pay Kitely for a Premium account ($19.95 per month) or for a fixed-price Starter World ($14.95 per full month); this works out at 300 KC per dollar.Kitely Credits
Kitely Credits (KC) are a virtual currency. You use KC to buy virtual goods and services.
Kitely Credits can't be converted back to real money, but they can be used to pay Kitely for its services. Merchants can earn real money by selling virtual goods for US Dollars in Kitely Market.