I've just submitted v1.1.0 of this plugin to the Zen Cart Plugins for review ...

If your store has downloadable and/or virtual products, it's possible -- depending on your configuration -- for a customer to add multiple copies of the product to their cart. The customer can go through checkout confirmation, paying for the quantity present in their cart ... but when it comes to the download itself, only one copy is available for the customer to download.

Downloadable/virtual products can fall into three different customization types:
  1. The product is configured with a single attribute, e.g. one that specifies the download filename. For this type of product, you can use the built-in Zen Cart methods to limit the product to a single instance in a customer's cart. Use your admin's Catalog->Categories/Products and set:
    • Product Qty. Minimum to 1
    • Product Qty. Maximum to 1
    • Product Qty. Units to 1
  2. The product can be purchased either as a download or as a physical (e.g. printed) item. For this type of product, you probably want to allow multiple copies of the physical product to be placed into a customer's cart. Unfortunately, with this configuration the customer can also place multiple copies of the download version of the product in his/her cart ... possibly resulting in charge-back issues for your store.
  3. The downloadable/virtual product has multiple configurations, i.e. more than one attribute. For example, the product might be available in more than one language or in different file formats. The customer should be able to have different configurations of the product in his/her cart, but limited to a single instance for a specific attribute combination.


This plugin addresses customization types 2 and 3 described above and can be downloaded from: http://www.zen-cart.com/downloads.php?do=file&id=1018