Chouby on "[Plugin: Polylang] Best way to pragmatically add a post in a language?"

That should work:

global $polylang;

$post = array (
	'post_author' => $user_id,
	'post_type' => 'jnet_member'
);
$result_en = wp_insert_post ( $post, true );
$result_ja = wp_insert_post ( $post, true );

$polylang->model->set_post_language($result_en, 'en');
$polylang->model->set_post_language($result_ja, 'ja');
$polylang->model->save_translations('post', $result_ja, array('en' => $result_en));