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. This plugin has not been published officially yet. The plugin author gave this codes in a support ticket. So don't rellay on it completely. 
Version: 1.1
Author: Pippin Williamson 
Author URI: http://pippinsplugins.com
Contributors: mordauk , oneTarek
*/
#Tested and working fine for me. 
#Bug fix: Able to check when site limit set to 0 means unlimited.

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

  $variable_pricing 	= edd_has_variable_prices( $download_id );
  if(!$variable_pricing){return $ret;} #we want this filter only for varibale pricing option.
  
  $prices = edd_get_variable_prices( $download_id );
  $limit_list=array();
  foreach($prices as $price)
  {
  	if(isset($price['limit'])){$lim=absint($price['limit']);}else{$lim=0;}
	$limit_list[]=$lim;
  }
  
	
  $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 ) {

		if(isset($limit_list[$price_id]))
		{
			$limit =$limit_list[$price_id];
		}#else no change of $limit
		
		$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
			}
			else
			{
				$ret=false; // license is not at limit . Added by oneTarek
			}
		}
		else
		{
			$ret=false; // license is not at limit. When limit=0 Licesne is for unlimited usages. Added by oneTarek
		}
	}

	return $ret;

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

#=================================================================================
function otk_edd_download_price_table_head($post_id=0)
{
echo '<th>Site Limit <span title="Set the limitation of how many website a single liecnse can be used in. Put 0 for unlimited website" style="color:#0074A2; cursor:pointer">(?)</a></th>';
}

add_action('edd_download_price_table_head', 'otk_edd_download_price_table_head', 10, 1);

function otk_edd_price_row_args($args, $value)
{
//echo "<pre>"; print_r($args); echo "</pre>";
if(isset($value['limit'])){$limit=absint($value['limit']);}else{$limit=1;}
$args['limit']=$limit;
return $args;
}

add_filter('edd_price_row_args', 'otk_edd_price_row_args', 10, 2);


function otk_edd_download_price_table_row($post_id, $key, $args)
{
 
$limit=absint($args['limit']);
?>
<td><input type="text" name="edd_variable_prices[<?php echo $key; ?>][limit]" id="edd_variable_prices[<?php echo $key; ?>][limit]" value="<?php echo  $limit; ?>" size="3" style="width:100%"/></td>
<?php 

}
add_action('edd_download_price_table_row', 'otk_edd_download_price_table_row', 10, 3 );

?>