Programmatically loaded taxonomy form ajax errors
This function worked for me:
Please try to use form_load_include() and drupal_build_form() instead of drupal_get_form() to generate form

  $form_id = 'taxonomy_form_term';
  $vocabulary = taxonomy_vocabulary_load($tid);

  $form_state = array();
  $form_state['build_info']['args'] = array($vocabulary);

  // use form_load_include() and drupal_build_form() instead of drupal_get_form()
  form_load_include($form_state, 'inc', 'taxonomy', 'taxonomy.admin');

  $form = drupal_build_form($form_id, $form_state);