Do people speak Flemish in Belgium?

I discovered a pretty posh magazine which apparently did only come out for one issue and I doubt that there was ever a second one. But there I discovered the Flemish author Geert Van Istendael who was arguing for a proud pro-belgian and anti-separatistic attitude. He is backed up in this essay by Herbert van Uffelen, who is giving a closer look on the language differences: In Belgien spricht man belgisch. (Yes, that's German, to add another tongue.)

I always like to read a bit more in-depth when I'm home from travel...