Target Audience selection

I created a small module that adds a "target audience" property for each amazon node. When someone edits the amazon node, s/he is able to tick checkboxes to specify the target audience for the amazon item, by default it is "Beginner, Intermediate, Advanced", but this is configurable in the module's settings.
The <theme>_amazon_node function needs to be created/modified in order to display the target audience, here is mine with zen theme:

/**
  * Custom amazon_node display
  */
function zen_amazon_node($node) {
  $module_dir = drupal_get_path('module', 'amazon');
  $output = '';
  $output .= '<table class="amazontools_table">';
  $output .= '<tr>';
  $output .= "<td><a href=\"$node->detailpageurl\" target=\"_blank\">";
  if ($node->mediumimageurl) {
    $output .= "<img src=\"$node->mediumimageurl\" height=\"$node->mediumimageheight\" width=\"$node->mediumimagewidth\" alt=\"cover of $node->title\" />";
  }
  else {
    $output .= "<img src=\"$module_dir/images/missingm.gif\" height=\"150\" width=\"100\" alt=\"no image\" />";
  }
  $output .= "</a></td><td>";
  if ($node->type == 'amazon') {
    if ($node->detailpageurl) {
      $output .= "<a href=\"$node->detailpageurl\" target=\"_blank\">";
    }
    $output .= $node->product_title . '<br /><br />';
    if ($node->detailpageurl) {
      $output .= '</a>';
    }
  }
  if ($node->author) {
    $output .= 'author: ' . implode('<br />', $node->author) . '<br />';
  }

  if ($node->rating) {
    $output .= "rating: <img src=\"/$module_dir/images/rating$node->rating.gif\" alt=\"\" /><br />";
  }

  if ($node->asin) {
    $output .= 'asin: ' . $node->asin . '<br />';
  }
  if ($node->binding) {
    $output .= "binding: $node->binding <br />";
  }
  if ($node->listformattedprice) {
    $output .= "list price: $node->listformattedprice $node->listcurrencycode <br />";
  }
  if ($node->formattedprice) {
    $output .= "amazon price: $node->formattedprice $node->currencycode<br /><br />";
  }

  $audience = db_fetch_object(db_query("SELECT audience FROM {amazon_audience_items} WHERE nid = '%d'", $node->nid));
  if ($audience) {
    $result = db_query("SELECT aid, name FROM {amazon_audiences}");
    $audiences = array();
    while ($row = db_fetch_object($result)) {
      if (_amazon_audience_book($audience->audience, $row->aid)) {
        $audiences[] = $row->name;
      }
    }

    if (count($audiences)) {
      $output .= "Target audience: ". implode(", ", $audiences) ."<br clear=\"all\" />";
    }
  }
  
  $output .= '</td>';
  $output .= '</tr>';
  $output .= '</table><br />';
  return $output;
}

See the attached tar.gz archive for the amazon_audience module.