Hmm...poking around in my demo folder on Ubuntu...
Seems to me that most of the files from later chapters aren't included, such as balls and levels. However, some stray files seem to be... such as ish images in res/images/levelimages. Strange.
Also included are res/islands/(all the island .bin files), but in res/levels, only island1 and island2 are there (island2 is a placeholder; you go there, and all there is is a button on a signpost leading to 2DBoy's website). It also includes fonts (like the console font) only used in later chapters, animations only used in later chapters, but not the movies from later chapters. Also no music from the later chapters.
So, it's pretty much stripped down. Hope this helps!

The console text is actually used for the WoG corp sign in World of goo corp, right next to your tower. (World of goo public terminal)

Ah, okay.

My friend just became addicted to goo, and I gave him the download link for the demo. I was wondering what I would have to do to make the AP demo work with the original game demo.

Well, theoretically if you made all custom balls and resources, it should work, if you only use your custom stuff.
James: good point. Forgot about that text...