How can user add new terms when using programatically???

How can user add new terms when using programatically????.

Im using as

$form['keywords'] = array(
            '#title' => t('Keywords:'),
            '#type' => 'autocomplete_deluxe',
            '#autocomplete_deluxe_path' => url('autocomplete_deluxe/taxonomy/field_tags', array('absolute' => TRUE)),
            '#multiple' => TRUE,
            '#autocomplete_min_length' => 0,
            '#default_value' => $default,
            '#autocomplete_multiple_delimiter' => ',',
        );

can any body suggest me.