Display categories in info window

You are using the correct filter, but you will first have to include the returned term data in the search data.

This code will do that for you, just add it to the functions.php in your theme folder.

Once you have done that you can access the term data in the wpsl_info_window_template filter like this.

$info_window_template .= "\t\t\t" . '<% if ( terms ) { %>' . "\r\n";
$info_window_template .= "\t\t\t" . '<span><%= terms %></span>' . "\r\n";
$info_window_template .= "\t\t\t" . '<% } %>' . "\r\n";