These are not official releases, these are automated builds from the master Git branch for testing. Builds are performed on OS X Server 10.6.8, Xcode 3.2.6, using the build script: code/tools/make_munki_mpkg.sh.
There is a download-and-install script available to get and install the tools in one step. Run the following command in a terminal session:
curl http://munkibuilds.org/latest.sh | sh
Contact the auto-build