WPMU DEV Events+ plugin - This snippet will count and return the active events.

active_events_count.php

<?php 
function get_active_events_count(){
	global $wpdb;

	$count =  $wpdb->get_var(
							$wpdb->prepare(
									"SELECT count(*) 
									FROM  $wpdb->postmeta
									WHERE meta_key = %s 
									and meta_value = %s ",
								'incsub_event_status',
								'open'
								)
							);
	return $count;
}