Well, if people register a forum account, they are at least interested in the game and its community. That's a good start, and kicking out people with zero posts would be a little rude. Those who post have an active interest in the game, but Glest is a "work in progress", and there isn't that much to post about yet. Once it offers a multiplayer-mode, I'm sure the traffic will increase, but at this point it is still an unfinished product. It is very playable already, but the "casual gamer" is more interested in finished games that come with a tutorial and a campaign than in a game that works greatly, but isn't quite done yet and doesn't feature more than what is essentially a skirmish mode.
Then again, look back a year and you'll see how much Glest has progressed. The game's a gem, a bit rough around the edges, but there is a huge potential. I don' really like to separate "open source"/free games and commercial titles, because at the end of the day it doesn't matter if a game costs money or not -- what does matter is whether or not it's fun to play. Still, it is developed in the spare time of those who contribute, and that means that it's growing more slowly than some commercial games whose developers have budgets of millions of dollars. Currently, I alpha-test a "million dollars" strategy game that will come out end of the year and that is developed by nearly 40 people, many of them with two decades of professional experience, all of them fully paid -- and let me tell you, the alpha-version is far beyond what Glest offers now already. Still, people work on Glest in their free time. That means that things will take time, and the community will grow slowly. The more development progresses, the more people will check Glest out, and the more will stay around and post. It's just a matter of patience.
Yes, it needs a MP modus, but I'm sure the devs are really tired of hearing this. *g* Well, actually, some of the popular open-source games are so popular because they allow for easily created user-content (scenario editor) and MP mode, like "Battle for Wesnoth", and I do think that this is a weakness of Glest at this point in time (that you need to know C++ in order to contribute). Then again, name any other open-source real-time strategy game that you can install and "just play", and have hours of fun with. I can't think of anything but Glest.
In short, let's be patient. Open-source games don't receive the same "hype" as commercial games and there aren't budgets of millions of dollars driving the development (and the marketing), but as long as we, and the developers, are having fun and a good time, all is well!