Start by creating a new build plan:

Select JRuby Releases Project:

Enter the release name and key:

Start key with a 'V'.

Choose a previous release build to clone:

Click next.

On the source repository page, change the URL to the release tag URL

Click next through the remaining screens.

That's it! If the build is successful, the artifacts will be deployed to the codehaus repository, which eventually is synched to the central maven repository.