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
Anyone working with code in the WordPress TinyMCE WYSIWYG editor will have had their code blown away when switching between “Text” (HTML) and Visual editing modes.
One of the many uses of Advanced Custom Fields plugin is to create a text area to stash code associated with a page or post that the editor can’t touch.
This serves to only store the code alongside the post/page in the database.
This will not prevent the editor from modifying the code again in the future if it is pasted back into the editor, but it is a convenient place to copy the code from again.
If you want a more permanent solution you could disable the visual editor, remove the filtering, or other options.