I'm not sure if Delphi users have free forum like freepascal.org, Embarcadero.com is more based on the commercial sphere (databases). Surely there is a difference between FPC and Delphi in many aspects, but all dll bindings are universal or they can be written as universal (Box2D, SDL, SFML, OpenAL or another audio visual libraries). I think most of this stuff is published only here (except their home sites like GitHub). This forum is currently the place where it all comes to public, it have same bonunes.
Ambitious projects like PGD requires a lot of effort and work from the authors, simply influx of new people must be higher than common loss in some period of time. Next thing is that they haven't any base element. Here it's development of FPC/Lazarus which is something tangible and it generates new users somehow. "We are programming games in Pascal" seems vague (and no one is promoting it either). In my opinion, the interest of language-specific pages like PGD should be an effort to cover different projects which can be extra value. Like why Castle engine and ZenGL have own forums? You can be with us and have bigger audience and more users. Or something in that sense.
@Ñuño_Martínez: 3x posts on main page (2017), 2x (2016) and forum is something like max. 10 posts per month? It's sad but..