re: Is there a charge to use this after the initial $19.99 is paid?
There is an option, but recommended, annual renew fee. The initial purchase you’ll get a year of updates and support for Gridder. After that year, you can, optionally, choose to renew the support license for continued support and updates. Gridder will continue to function if you choose not to (unless there is a breaking change in Connections which I avoid doing).
Hope that answers your question thoroughly.