Remove the word "free" from free products
<?php
/*
 * Plugin Name: Easy Digital Downloads - Remove Free Text
 * Description: Remove the word "free" from free products
 * Author: Easy Digital Downloads
 * Author URI: https://easydigitaldownloads.com/
 * Version: 1.0
 */

function pw_edd_remove_free( $form, $args ) {
	
	$form = str_replace( 'Free&nbsp;&ndash;&nbsp;Add to Cart', 'Add to Cart' , $form );

	return $form;
}
add_filter( 'edd_purchase_download_form', 'pw_edd_remove_free', 10, 2 );
To implement this snippet on your site, create a brand new, empty WordPress plugin and paste the above code inside.