How to open .packproj files?

I am unable to run an installer with .packproj extension. I am unable to find anything via Web search.

Can these files be handled natively by macOS? How do I install a package with this extension?

Solution 1:

.packproj-files were files used by developers in the process of application development for OS X 10.2. They contain xml-strings – try editing the file in TextEdit or TextWrangler, you should see an XML-structure, or see this example.

It can't really be run alone, it's used to tell packaging applications how to pack the application into a real application.

To put it short, it can be used with the application Iceberg:

(.packproj): Creates a project file for use with Iceberg. This allows you to use Iceberg to edit package options before creating the actual package.

Do note that this is ancient code, and may not work (supposed to work from OS X 10.2 and up).