Maven release plugin was part of the main maven package in the time of Maven
2.0.4 but it has moved in a separate project after that and noone found the
time to package it. You can find the new project here
http://svn.apache.org/viewvc/maven/release/tags/maven-release-2.0/. It
contains both maven-release-plugin and maven-release-manager and they have to
be packaged together.
I'll be more than thankful if you prepare such package.
Alex