If this is the book that FogCreek gave to new developers, those developers would have been told "Wasabi's our internal dialect of BASIC; and we added functional programming language features to it."
You have to try pretty hard: the compiler and runtime are available in closed-source form for FogBugz For Your Server installations, in the Accessories directory.
I'm also planning on open sourcing the new Roslyn-based code generator. I don't currently have any plans to open-source the rest of it.