The forms in there are really over simplified, but you would enter the product data in the top portion of the form. The lower portion (with tabs) would contain data in regards to the user or user(s) as you can key multiple lines of information per product under the user tab.

Also I removed the field licenses available from the product table (I believe), as you can create a couple of calcuated fields on the reports to indicate how many have been used, and how many are still available.

Your .NET approach sounds very interesting, sounds like I need to take a couple of courses before I am totally left behind!