Which functions are you asking about? ChipmunkDemoFreeSpaceChildren() is a function only defined in the demo app, postBodyFree(), etc are static functions that are only defined for ChipmunkDemo.c. If you want to use these functions, you'll have to copy the declarations into your program.
The cpSpace*() functions they call are part of Chipmunk though.
One more thing to keep in mind is that you must track any rogue or static bodies you create in your own code. Since they are never added to a cpSpace, you can't use a Chipmunk space to manage them. Chipmunk spaces aren't meant to be collection classes to help manage memory. They are only meant to perform simulations and queries.