Backport to v5?

I would like to add my vote for that.

I tried the module in V5.x and it seems to work if you change the hook_menu().

/**
 * Implementation of hook_menu().
 */
function sharethis_menu() {
  $items[] = array(
    'path' => 'admin/settings/share-this',
    'title' => t('Share This Settings'),
    'description' => t('Administer settings related to the Share This module.'),
    'callback' => 'drupal_get_form',
    'callback arguments' => array('sharethis_admin_settings'),
    'access' => user_access('administer share'),
    'type' => MENU_NORMAL_ITEM,
  );
  return $items;
}

Use this code at your own risk :-) No guarantees at all.

The Share module provides the ability to use ShareThis. There is a newer version of the Share module which will allow for more customizing of ShareThis but is not yet public.

http://drupal.org/project/share

Yes, http://drupal.org/project/share is recommended for D5