What happened to the other Forerunners?

Question

MAJOR SPOILERS

In the recent novel HALO: Silentium, it was revealed that

The Forerunners rose up and exterminated the Precursors, but they were so ashamed that the assault force relinquished their weapons and stayed on Path Kethona (another galaxy, to us the Large Magellanic Cloud)

Also, at the end of Silentium, the Librarian is on Earth, creating the Portal discovered in HALO 3, but

she may have survived, as she appears to be talking after the effects reach Earth.

Halo.wikia says:

According to 343 Guilty Spark, at least the The Librarian is alive, and he knows where to find her. It has been said that the remaining Forerunners made an exodus out of the Milky Way Galaxy to which no one knows their current fate.

Somehow the Didact survived the Halo firing, though whether that was because he was in his Cryptum or because Requiem was similar to a Shield World, or for some other reason we don't know.

So what happened to these Forerunners? Were some of them out of range of the Halo Array when they fired? Is it possible that some were somehow able to shield themselves from its effects?

Answer 1

That's covered in Silentium, and a summary is here. A quote:

During the final stages of the Battle of the greater Ark, Omega Halo was fired in an attempt to stop the advance of the Precursor star roads. While decimating a small portion of the star roads, the blast also purged the satellite galaxy of all sentient life, while the star roads ended up destroying Omega Halo and the greater Ark anyway. Thus it is highly probable that the Path Kethona Forerunners were annihilated by the Halo blast and since it is not known if any of them were indexed or taken back with the Librarian, the subspecies has been rendered effectively extinct.

Not a happy ending, as they seemed like nice folks, but there's your answer.

As for the other Forerunners, apart from The Ur-Didact, I don't know of any that survived. While slipspace disruption would have affected space travel, there's no reason they wouldn't be on other shield worlds. While that's not known at the moment, The Librarian's data (which the Covenant had one half of and the humans had the other) has the location of all Forerunner artifacts. But neither side can access it without the other half. This was in the episodes for the Spartan Ops in Halo 4. I suspect we'll run across some more Forerunners in the remaining fiction, as it's too good a plot point to turn down.

Answer 2

When 343 Guilty Spark turned bad in Halo 3, this is what it said to Master Chief:

"You are the child of my makers. Inheritor of all they left behind. You are Forerunner! But this ring... is mine."

It says that Mankind is the Forerunner. As for technology differences, it's possible that we lost all of our ancient technologies (possibly when the Halo array was fired for the first time). This explains why only a human could start or stop Halo weapon array on the Ark and a device which could open a portal to the Ark existed on Earth.