Bring back the customers who have abandoned the cart due to any reason. Send them an automatic email encouraging the customers that they have left some product in their cart. If the user is unregistered, but he has entered his email id in the respective field, then you get an option to send an email to the guest also. This marketing technique can improve your sale up to 300% in most of the cases.
The idea behind GPLDownloads is to help website owners or small developers who have enough knowledge and experience of WordPress that they do not need technical support that developers provide or who are running low on budget & need to buy the plugins for their own and clients projects.
This is the same plugin or theme as distributed by the developer, the developer link is provided above.