Removing the * to denote required fields and marking all optional fields as "optional" in Drupal

formutils.module

function formutils_form_alter(&$form, &$form_state, $form_id) {
  if (is_array($form['submitted'])) {
    foreach ($form['submitted'] as $field) {
      if (!$field['#required']) {
        $currentTitle = $field['#title'];
        $field['#title'] = $currentTitle . ' (optional)';
      }
    }
  }
}