This is not a CodeIgniter library, but a complete CodeIgniter application built by Derek Allard. Why have we added it here? Well there are two reasons. First, it's a great example of what can be built with CI—powerful sites and applications. Second, it's a useful application that you can use to take care of your invoices. As Derek says, you have your data on your own server, be it a shared one or local, so you are not sharing your data with a third-party company.
Take a look at what it looks like:
Doesn't it look great? A good example of what can be done with CodeIgniter. Take a look at it here http://bambooinvoice.org/.