Shenandoah has been accepted as OpenJDK project.
Shenandoah will use OpenJDK infrastructure for hosting Shenandoah development:
Use http://mail.openjdk.java.net/mailman/listinfo/shenandoah-dev as mailing list for discussions and development.
Code repositories are http://hg.openjdk.java.net/shenandoah
You will notice that there's a JDK9 and JDK8 branch in there. Both will be maintained.
The Mercurial history will remain on Icedtea servers, should anybody be interested in it.