The terms are not clearly defined in any sort of fashion that is agreed upon. Remember that Keith and I come from software backgrounds outside the industry, too. The way that I tend to use the terms is:
1. Alpha is something that is not yet feature-complete.
2. Beta is, but is not done.
In this particular case I would already call this beta, aside from quests not really having enough content yet. So likely we'll just stay "alpha" in terminology until release. Why the heck not, at this point.
Better than switching terms a few days before release, because that really would raise eyebrows.
When this first started, back in January, it was truly an alpha in every sense. Somewhere along, not that long ago, that changed. Things move fast!