You will always have control of your content’s copyright even after you sell it. The Whoosnap Marketplace consents you to sell a license, merely giving the buyer rights to use the content.
The pictures shot through Whoosnap can’t be saved in your smartphone gallery, and therefore can’t be sold on other platforms. They can be shared on Whoosnap though.
Regarding the pictures shot with your phone and uploaded on Whoosnap from your smartphone’s gallery, you can use them with complete freedom and use them on other platforms.