It's hopefully going to be more like what Firefall was originally intended to be (NOT WOW with guns). Similar in combat mechanics and other things that people enjoyed from Firefall, before it got so messed up.
And several former red5 devs are working on this game in their freetime besides their own job.
It will take a while before Ember has a fulltime dev team
Yes, there are devs from there on this (potential) project.
Firefall had an original vision in beta which did not make it into the release. That, at least in part, is that @Grummz is interested in. So therefore it has differences from Firefall.