I think it would be cool if Blizzard supported legacy servers. If they still had the code, I really don't care if most of the team isn't currently with the company. Why does that matter at all? I think the whole point of desiring this is simply to have more security that your characters won't vanish suddenly.
Is Nost a fly by night operation? It doesn't seem like it, but still, our characters are not as secure as they would be if supported by Blizzard.
That all said, even if Blizzard supported them, Nost does at least have a superior management philosophy in terms of coming down hard on cheaters.
If you want this place to be more secure long-term, maybe pitch in and help them out. I think burn-out of the management team is the biggest risk. If the community pitches in and takes a lot of the pressure off, it makes it that much easier to run this place long-term.