Red Hat has just released a beta version of Subscription Asset Manager. It is a new tool which is available with your subscription. The tool allows you to do on premise Subscription Management. You can see the Quick Start guide at the website.
This is the first product to come out of the great work which the team is doing on Candlepin, Katello, and Thumbslug. If you are an open source project looking to add subscription management functionality, you should stop on bye and take a look.