I would like some wp_die messages to be translatable, so I changed a download.php:175 (or 174) to:
wp_die( sprintf(__('You must be logged in to download this file. <br/><br/><a href="%1$s"><strong>← Back to %2$s</strong></a>', "wp-download_monitor"), get_bloginfo('url'), get_bloginfo('name')), __('You must be logged in to download this file.',"wp-download_monitor"));
Any chance that you would apply that change to your code?