function my_function( $can_access, $user_id, $post_id ) {

    if ( isset( $_GET['onething'] ) {
        $can_access = true;
    }

    if ( isset( $_GET['something_else'] ) {
        $can_access = true;
    }

    if ( isset( $_GET['a_third_thing'] ) {
        $can_access = true;
    }

    return $can_access;

}

add_action( 'wpf_user_can_access', 'my_function', 10, 3 );