Thank you for this great module. Have you any plans using the Joomla system plugin for providing captcha functionality? This way the admin can install any captcha solution that is appropriate for the website like a more advanced and hidden captcha (which works independent from Google).
At the moment, we haven't any plan to implement the Joomla Captcha feature in the module. It uses an "own Captcha" system (not dependent from Google) and, for now, we have not many requests to implement other Captchas.
Anyway, we can insert the task in pur todo list, maybe in the future versions if the module, we will implement it. Besides I can't ensure the implementation now.
Implementing the Joomla Captcha feature in the module would be great since there are sophisticated captcha plugins that dont require any user interaction which enhances the user experience drastically.