To simply put it, it allows for you to give attributes a quantity. I
know a few people that use this shopping cart that wished that it had
this option so I thought I would write a modification to do this.
Once you have added an attribute the quantity option for the actual
product is disabled. This mod will control your product stock levels
so everytime you add or delete a product attribute the total quantity
will change accordingly. If you delete all attributes for a certain
product you will have access to the standard quantity control again.
Once a product attribute has reached a quantity of 0 it removes the
product attribute from the product page. Future development might
include more options for this.
Thanks to Pavel Rojkov I have added his contribution to allow you
to manage product attributes from the products page.