You must misunderstood something then because purchase codes (license keys) are not included for plugins which are bundled into theme. It’s because of Themeforest license & agreements. This applies to all themes of course. However, there is no need to use this code because the plugins are fully functional without it. If you want, you can read more details about this on Envato forum:
Comments
what exactly you want to register? And what for?
http://themeforest.net/forums/thread/dont-work-my-purchase-code-stardust-w-revolution-slider/186285