pkg-dmg is tri-licensed under the MPL/GPL/LGPL.  It was originally written
for the Mozilla project, which no longer uses it. The final revision of the
Mozilla version is available at:

https://hg-edge.mozilla.org/mozilla-central/file/3e51753a099f8014b3dc37ed3fa27b887842735b/build/package/mac_osx/pkg-dmg

and its revision history is available at:
https://hg-edge.mozilla.org/mozilla-central/log/tip/build/package/mac_osx/pkg-dmg