edd.php

<?php
//license limit
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;
        break;
      case 1:
        $limit = 2;
        break;
      case 2:
        $limit = 3;
        break;
      case 3:
        $limit = 4;
        break;
      case 4:
        $limit = 5;
        break;
      case 5:
        $limit = 6;
        break;
      case 6:
        $limit = 7;
        break;
      case 7:
        $limit = 8;
        break;
      case 8:
        $limit = 9;
        break;
      case 9:
        $limit = 10;
        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
      } else {
        $ret = false;
      }
    }
  }
  return $ret;

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