Source packages feature is documented here: https://github.com/dazinator/DnnPackager/wiki/Sources-zip-package
Thanks @nvisionative for requesting this feature.
In short, DnnPackager will now output a "sources" version of your install zip alongside the ordinary install zip (in the bin directory).
A source file, is any file in the project that has a "build action" set to "compile".
In VS, in the package console manager window,
Install-Module command will install the ordinary zip as before. If you want to install the sources version of your package instead, use the new
Install-ModuleSources command. Both commands have the same arguments. Info on wiki here: https://github.com/dazinator/DnnPackager/wiki/Package-Manager-Console-Commands