When you purchase a code from this site, you're actually purchasing a license. What that means is that you purchased the rights to re-skin the code. If you purchase a single license, you have the right to re-skin and publish the code one time under your name. If you purchase an unlimited license, you can publish as many as you wish.
A license, however, does not give you the rights to re-sell your app with the full rights. Any sale you make has to include the original terms of a license.
Example: Mary purchases the Kingdom Roulette source code from this website. She re-skins it and makes a very successful app. Mark approaches her and wants to buy the app from her. Mary can sell the app to Mark, but Mark can only make copies of the app in the same way Mary could. Similarly, Mark nor Mary can sell licenses of the code to others (because technically none of them "own" the code, they just own the licenses).