Great Module, thanks.  
	I had some luck getting this to integrate with FormBuilder (method d) by using the following Form Builder hook to check the recaptcha before submitting:
 
$forms->addHookBefore('FormBuilderProcessor::processInputDone', function ($e) use ($captcha) {
$form = $e->arguments(0); // retrieve argument by number (zero based)
    // Check to see if recaptcha is true
	if ($captcha->verifyResponse() === true) {
        // This will process the form as usual
	} else { 
        // This will cause an error on form and stop processing 
        $form->error('Recaptcha is missing. Please tick I\'m not a robot and try again');
	}
});
	More info on FormBuilder hooks: https://processwire.com/blog/posts/formbuilder-v34/  
	Cheers,