We've accumulated too many patches/fixups/etc... to keep our sanity, so
rpm2targz is now maintained in a git repo which we make releases from (so
hopefully other distros can take advantage of things).

You can find that repository here:
http://git.overlays.gentoo.org/gitweb/?p=proj/rpm2targz.git;a=summary

The versioning schema is simple.  Just append '.0.#g' to the upstream version
(which in this case is '9.0').  Increment the '#' over time.  The 'g' is short
for Gentoo.  Awesome.