Minor version updates (eg Infiltrator 2.0->2.1) are always free. This includes support for bug fixes, general improvements, and occasional new features. We also have provided larger updates with batches of new features completely free-of-charge. Duck 2 is the first time we have charged an upgrade fee. It is not a general policy we have, but we reserve the right to charge an upgrade fee for a major new version of a product (e.g. Duck 1->2)
Since we are aware of some... "industry practices" around charging customers for products that they paid for. I hope we can put your mind at ease that this is the last thing that we want to do. If you have any concerns at all, please send us an email at support@deviousmachines.com