Invoicing made simple

[Bill]

Has anyone written an invoicing stack? Ideally with a mySQL database -- that
has lots of commenting in the code and could easily be integrated into other
renrev applications. There is a filemaker pro invoice program that is called
blue box which would be wonderful ported to runrev. And the sell the source
code version cheaply. http://www.blueboxsw.com/

Intuit's Quick books pro has included invoicing but it is not customizable
and other accounting programs that don't have invoicing such as Intuit's
Quicken 2005 for some un-accountable reason have more features (like online
banking).