For such a simple application (pane with 20 controls and a GO button, 2k lines of code), I think Lazarus (or Delphi) are fantastic solutions.

Either of these two would give you Windows, Mac, and Linux coverage for your app (and in the case of Delphi, also mobile apps).

* Lazarus - https://www.lazarus-ide.org

* Delphi - https://www.embarcadero.com/products/delphi