Allow duplicate email address with User Registration

<?php
// Author: David Smith
// http://www.gravityhelp.com/forums/topic/disable-duplicate-email-check-snippet#post-91521
// http://www.gravityhelp.com/forums/topic/multisite-register-users?replies=2#post-129695
/**
* Gravity Forms User Registration validates a number of fields. This snippet allows you to override the validation for
* duplicate emails. This is useful when using the "Allow Multiple Accounts" plugin.
*/
add_filter('gform_user_registration_validation', 'unvalidate_duplicate_email', 10, 2);
function unvalidate_duplicate_email($form, $config) {
    // update the 1 here to your form ID
    if($form['id'] != 1)
        return $form;


    $email_field_id = rgars($config, 'meta/email');
    foreach($form['fields'] as &$field) {
        if($field['id'] == $email_field_id && $field['validation_message'] == 'This email address is already registered')
            $field['failed_validation'] = false;
    }

    return $form;
}