I would like to know what formatting the InstallBuilder project file is using.
The format of InstallBuilder project files is XML. This makes it easy to manipulate with scripts and integrate in source control systems. The XML structure of the file and naming of tags has been designed to be human-friendly, meaning that it is easy to edit by hand as well. In fact, many of our customers prefer to do so, especially for complex projects. You can see a sample installer project in the Appendix of the documentation included with the product.