Yes, as long as the major version number (the first digit) is the same, there is no charge.
For example, you can upgrade from WebDirect 1.1.3 to 1.1.7 without any additional fee.
Should the major version ever be updated to 2.x, then it would signify a new product. You would need to purchase a new license if you want to use the 2.x version. Even in this case, we would still provide support and security updates (if any) to the older 1.x versions.
To download the latest version of a licensed product, please use the original download link from your receipt email, or contact customerservice@collectivesoftware.com if you no longer possess a copy of that information.