Checked in on this mod yesterday and found a cool Arachnotron pic:
Apparently the mod is still alive and being worked on, though a playable release still hasn't happened. The devs have chimed in since Doom 4's release to explain how their version of Doom will be different:
Our type of “old school” is a very different breed than the type encountered in today’s “old school”. Yes, there are similarities; We too have upped the action, speed and gore, but not to the extreme lengths seen in the new Doom game. Our levels are built for exploration, progression and environmental puzzles. These are our main qualities. Phobos is closer to games like Half-Life or Dark Forces/Jedi Knight in spirit. Just like Classic Doom, these games are types of First Person Shooters that have all but vanished. We truly are a different kind of oldschool.
There are also a couple tiny clips of in-game footage and some new screens.