Offer a checkbox to get a copy of autoResponder or not

<?php
// http://www.gravityhelp.com/forums/topic/checkbox-on-form-for-confirmation-email#post-116946
// change the 243 here to your form ID
add_action('gform_pre_submission_filter_243', 'notification_preference');
function notification_preference($form) {
    // this will enable a checkbox to confirm receipt of the autoresponder which is
    // already configured.  If it is not set, then clear the autoresponder array
    // input_4_1 is my checkbox, and I have enabled values and set the value to 'yes' if it is checked
    // change the input_4_1 to your field ID, and the 'yes' to whatever value you have set when this is checked/selected
    if (defined(rgpost('input_4_1')) && (rgpost('input_4_1') == 'yes')) {
        return $form;
    }
    else {
        // clear out any autoresponder values
        $form['autoResponder'] = array(
            'toField' => '',
            'bcc' => '',
            'fromName' => '',
            'from' => '',
            'replyTo' => '',
            'subject' => '',
            'message' => '',
            'disableAutoformat' => '');
        return $form;
    }
}