Reusing old items in other new items

Every item we upload on an Envato platforms ( ThemeForest, Codecanyon… ) will be under that platform license ( or that’s is what I’ve been told ), in some rare cases the author needs to use his old item from Codecanyon in a new project in ThemeForest, for Example using a buttons and forms kit in a new WordPress theme or plugin, what would the action of using it be “authorized” Or “copyright violation”. and in case the item is very useful in other Codecanyon Projects can he use it again knowing that the output will be completely different in both cases because the item is used just as a start??

Assuming it is the original author and they own both items then I can’t see why it would be an issue.

Obviously if it’s using another author’s items then that’s very different


Thanks for the response, at less i feel more confident about starting this, thanks.