gistfile1.php

<?php
/*
Plugin Name: Easy Digital Downloads - Variable Pricing License Activation Limits
Plugin URL: http://easydigitaldownloads.com/extension/
Description: Limit the number of license activations permitted based on variable prices
Version: 1.0
Author: Pippin Williamson
Author URI: http://pippinsplugins.com
Contributors: mordauk
*/

function pw_edd_sl_license_at_limit( $ret = false, $license_id = 0, $limit = 0, $download_id = 0 ) {

  $purchase_id   = get_post_meta( $license_id, '_edd_sl_payment_id', true );
	$purchase_date = new DateTime( get_post_field( 'post_date', $purchase_id ) );
	$limit_date    = new DateTime( '2013-01-01' );

	if( $purchase_date < $limit_date ) {
		// licenses purchased before January 1, 2013 are unlimited
		return false;
	}

	$purchase_details = edd_get_payment_meta_cart_details( $purchase_id );

	$price_id = false;

	foreach( $purchase_details as $item ) {
		if( $item['id'] == $download_id ) {
			if( ! empty( $item['item_number']['options'] ) ) {
				foreach( $item['item_number']['options'] as $option ) {
					$price_id = (int) $option['price_id'];
				}
			}
		}
	}

	if( $price_id !== false ) {

		switch( $price_id ) {

			case 0:
				$limit = 1; // single site license
				break;
			case 1:
				$limit = 5; // up to 5 sites
				break;
			case 2:
				$limit = 0; // unlimited
				break;
		}

		$site_count = absint( get_post_meta( $license_id, '_edd_sl_site_count', true ) );

		// check to make sure a limit is in place
		if( $limit > 0 ) {
			if( $site_count >= absint( $limit ) ) {
				$ret = true; // license is at limit
			}
		}
	}

	return $ret;

}
add_filter( 'edd_sl_license_at_limit', 'pw_edd_sl_license_at_limit', 10, 4 );

So I've tested it and found the same results as @jgalea - licenses are still activated on my end more than the limit. The UI is nice but the API needs to return better results so we can output the information to the user such as "No activated, you have reach the limits (5) of your license... to purchase more yadda yadda..." and return the number of active licenses currently. Right now I can't rely on this patch to do the job.

Do I still need to add this code when we have the "License Activation Limit" setting in the Download Prices meta box?