ForumWP: How to extends the topic data

functions.php

function fmwp_topic_data_custom( $topic_args, $topic ) {
	$author = get_userdata( $topic->post_author );
	$topic_args['author_username'] = $author->user_login;

	if ( ! empty( $topic_args['people'] ) ) {
		foreach ( $topic_args['people'] as $people ) {
			$user = get_userdata( $people['id'] );

			if ( $topic->post_author == $people['id'] ) {
				$people['avatar']['title'] = sprintf( __( 'Created by %s', 'forumwp' ), $user->user_login );
			} else {
				$people['avatar']['title'] = sprintf( __( 'Last reply by %s', 'forumwp' ), $user->user_login );
			}
		}
	}
	$topic_args['people'] = $people;

	return $topic_args;
}
add_filter( 'fmwp_ajax_response_topic_args', 'fmwp_topic_data_custom', 10, 2 )

topic-row.php

Please use {{{<?php echo $item; ?>.author_username}}} to show the custom data