This is the replacement for gnome-fallback, a gnome session without 3d accelerated requirements.
Henrik tested this briefly on Ubuntu 13.10 but had problems with the panel. Might be because it needs to be started via upstart the same way as unity. Need to investigate more.
The project seems to be surviving and is trying to stay current with regular Gnome releases. I tried it on Fedora 25 and it worked well.