Only allow nodes to be posted to forums

It's mainly this bit of code:

// Loop through all bundles for forum taxonomy vocabulary field.
    $field = field_info_field('taxonomy_' . $vocabulary->machine_name);
    foreach ($field['bundles'] as $type) {
      // Check if the current user has the 'create' permission for this node type.
      if (node_access('create', $type)) {
        // Fetch the "General" name of the content type;
        // Push the link with title and url to the array.
        $forum_types[$type] = array('title' => t('Post new @node_type', array('@node_type' => node_type_get_name($type))), 'href' => 'node/add/' . str_replace('_', '-', $type) . '/' . $variables['tid']);
      }
    }

But also whether we want to try to lock down the forum vocabulary field so you can only ever apply it to nodes. I think that last bit requires a small change to field API though - although there's an issue somewhere iirc.