Hey Brian,
The best way to handle purchases is to generate the product key at the moment of the successful purchase. We show how to do it in several web programming languages, and we have pre-built examples: https://wyday.com/limelm/help/how-to-generate-product-keys-after-order/
The reason we don't have a Delphi example is because Delphi really isn't a web programming languages.
Of course, after you generate the product key you can use the product key in your app: https://wyday.com/limelm/help/using-turboactivate/