From http://phabricator.org/ : "Phabricator is a open source collection of web applications which make it easier to write, review, and share source code. It is currently available as an early release. Phabricator was developed at Facebook."
It's open source so pretty much anyone could host an instance of this software.
We will use this JIRA to deal with adding (and ensuring) Apache-friendly support that will allow us to do code reviews with Phabricator for HBase.