Wow, I'm surprised someone even found that. No matter, I updated that a bit ago:
http://www.hard-light.net/forums/index.php/topic,19567.0.htmlMuch more accurate and more full of information than the first. Enjoy.
As for subspace, I always have assumed that it meant the nodes. Once the tech is discovered and made widely available, I could see mass colonization from an overcrowded Sol system happening quite quickly (it did, obviously).
Of course the 14 Year War didn't completely consume the time of the Terrans and the Vasudans, both were probably busy exploring and colonizing while the front line troops fought it out. Considering that a good portion of the systems (Capella, Epsilon Pegasi, etc) were actually the systems in contention when the Shivans arrived, there were probably loads of people, mostly in the form of soliders and support, in each of those systems. When the Great War ended, they probably just settled down whereever they were since they weren't going home (Earth). That's probably how the majority of the systems became as quickly and massivily colonized as they were in FS2.
Though, if I remember right, there were only a couple hundred million people in Capella, so that's not really a lot considering the US has 300 million by itself.