Finally, there is a messy solution – I have to get all taxonomy terms (that are ordered by WP-Term-Order plugin). Then I have to get all post terms (unordered). And I extract those ordered terms that are connected to the post.
global $post;
$correctly_ordered_post_terms = array();
$used_terms = array();
$post_terms_unordered = get_the_terms( $post, 'my_taxonomy' );
// if( ! $post_terms_unordered ) return false; // post has no term
foreach( $post_terms_unordered as $post_term ) {
$used_terms[ $post_term->term_id ] = $post_term;
}
$all_taxonomy_terms_ordered = get_terms( 'my_taxonomy', array('orderby' => 'order') );
foreach( $all_taxonomy_terms_ordered as $ordered_term ) {
if( isset($used_terms[ $ordered_term->term_id ]) ) {
$correctly_ordered_post_terms[] = $used_terms[ $ordered_term->term_id ];
}
}
$correctly_ordered_post_terms // ... array with ordered post terms.