The short answer is no, not completely standalone.

You can make a plugin from the output of the Advanced Custom Fields’ export to PHP option, but it still requires that the site have the full Advanced Custom Fields plugin installed.

There is a way to hide the ACF plugin’s user interface by defining define( ‘ACF_LITE’, true ); before including the acf.php file.

For simple custom fields, you might be better off defining them through native WordPress code https://codex.wordpress.org/Custom_Fields