My impression is that the developers (or perhaps the remaining single developer, as mentioned elsewhere in this thread) has lost interest in maintaining it, rather than been unable to continue.
Wikimedia has been maintaining a phabricator fork for years and have sponsored upstream with monetary contributions on more than one occasion.
It doesn’t seem like there is much interest in finding ways to keep phacility alive.
Note: I work on phabricator at Wikimedia. My opinions do not necessarily match those of the foundation and I’m speaking from personal experience not from any position of authority.
My impression is that the developers (or perhaps the remaining single developer, as mentioned elsewhere in this thread) has lost interest in maintaining it, rather than been unable to continue.