Posts with specified tags will not require membership to view

open_tag_posts_to_all_visitors.php

<?php
/**
 * Posts with specified tags will not require membership to view 
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_open_tag_posts_to_all_visitors( $hasaccess, $thepost, $theuser, $post_membership_levels ) {

	// if PMPro says true already, return true
	if ( $hasaccess ) {
		return $hasaccess;
	}

	// Posts with these tags will be accessible to everyone
	$tags = array( 'free-tag' );

	if ( has_tag( $tags, $thepost ) ) {
		$hasaccess = true;
	}

	return $hasaccess;
}
add_filter( 'pmpro_has_membership_access_filter', 'my_pmpro_open_tag_posts_to_all_visitors', 20, 4 );