I don't know where all the free game developers are (and why not here). I mean, look at Github and you see a lot of activity on free games. But maybe they don't like to talk because they prefer coding. Don't know.
Just checked back in after a couple of months, and as someone who made an account recently but didn't stick around I think I might be able to answer the "why" from my perspective: To be perfectly frank, this doesn't feel like a good place for discussing game development.
If you browse through the forums a bit, you can see what kinds of threads attract discussion and what kinds attract dust. The vast majority of discussion is happening on "meta threads" talking about the forums (like this one!), and on threads about playing existing free games rather than making them. And from lurking in the IRC for the first few weeks, it was the same story there. For instance, of the 8 posts in Showcase active in the past two months, only 2(!!!) are being developed by forum members. Sharing cool games might be a nice thing to do, but the reality is that little to no gamedev discussion is ever going to happen on threads like these.
At the same time, this is also a super tech-focused community. You can tell by comparing the "Code Q&A", "Art & Assets", and "Game design" tags, the latter two are incredibly bare. I'd say this is not a good ratio for any gamedev community that's not focused on a specific piece of tech (like an engine's forums), since code is honestly not that important to the apparent quality of the finished product (Speaking as a professional game programmer, I realize the irony of that statement. But it's still true!).
But even discounting all of that, many coding-related discussions are less about any specific techniques or even largely gamedev-related: Most of them are about things like language / style / tool prefs, rather than discussions of actual gamedev.
In short: My suspicion is that gamedevs that find these forums quickly realize that they're not actually about gamedev at all, then leave.