List users that has not activated their account

<?php

function bp_rc_list_not_activated_users() {
    global $wpdb;

    if( is_multisite() ) {
        return $wpdb->get_results("SELECT user_email, activation_key FROM {$wpdb->signups} WHERE active = 0", OBJECT);
    } else {
        return $wpdb->get_results("SELECT user_email, meta_value as activation_key, user_id FROM {$wpdb->usermeta} m LEFT JOIN {$wpdb->users} a ON(m.user_id = a.ID)  WHERE meta_key = 'activation_key'", OBJECT);
    }
}

?>