"Forms that can be viewed" option does not work as it is described in the description.

In the "Read Only Mode" module's configuration page (/admin/config/development/maintenance),

Read Only Mode -> Allowed forms -> Forms that can be viewed

The description of the textarea (site_readonly_forms_viewonly) says:

These forms are allowed to be viewed but will not accept form submissions. Enter one form id per line. You may use the wildcard character '*' to use loose matches. For example: webform* will match all webforms. Note that the following forms will always be allowed: node_admin_content, comment_admin_overview.

But, if we enter the form id in that text area and then check the page having that form, we just see the warning message. All the form elements seems to be removed.

According the description, we should see all the form elements with submit event disabled.

function readonlymode_form_alter(&$form, $form_state, $form_id) {
  $mode = _readonlymode_form_check($form_id);
  if ($mode != READONLYMODE_FORM_ALLOWED) {
    // Check whether the form is a fresh form being served to the user.
    if (!isset($form_state['input']['form_token'])) {
      // If a redirect URL is set, then we redirect to it.
      if ($url = variable_get('site_readonly_url', '')) {
        drupal_goto($url);
      }
      else {
        // Replace FAPI #after_build handlers with our block form.
        $form['#after_build'] = array('readonlymode_block_form');
      }
    }
  }

  $path = current_path();
  if (user_access('readonlymode access forms') && variable_get('site_readonly', FALSE) && $path != 'admin/config/development/maintenance') {
    drupal_set_message(t('The site is currently set to read-only, content moderation is disabled for all users without the "Access all forms while in maintenance" permission. <a href="@link">Go online</a>.', array('@link' => url('admin/config/development/maintenance'))), 'warning', FALSE);
  }

  $form['#validate'][] = 'readonlymode_check_form_validate';
}

Seeing the codes, it looks like the constants READONLYMODE_FORM_DENIED and READONLYMODE_FORM_VIEWONLY are behaving the same. The result is also same if we remove the "Forms that can be viewed" option.