Source files?

[rapodaca]

It looks like the source files are in zip archives. However, using unzip utilities I'm not able to unzip them. On macOS:

$ unzip AssemblyMC.zip
Archive:  AssemblyMC.zip
  End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.
note:  AssemblyMC.zip may be a plain executable, not an archive
unzip:  cannot find zipfile directory in one of AssemblyMC.zip or
        AssemblyMC.zip.zip, and cannot find AssemblyMC.zip.ZIP, period.

How do I get to the source files and what's the reason for not putting them in the repo to begin with?