Actually that's exactly the point of this project. I run a startup called CoinJar (the first VC-backed Bitcoin startup in Australia) and Bitbillpay consumes CoinJar Checkout API.

I will open source the project once it has gained some initial traction. But before that, I will probably write a few tutorial-like blog posts to demonstrate how to integrate the seamless and unbranded Bitcoin checkout solution into any online business.

But of course, Bitbillpay is actually easier and faster to use than POSTbillpay. For one thing, you don't have to enter your credit number, and you can automatically receive an email with the receipt. (Australia Post will ask you to "print out".)