Pretty simple. Take out the correct lines in the AndroidManifest.xml, remove the library from the libs folder. You might get some complaints when you clean/build, but they should be easy to just comment out. An alternative would be Chartboost (see
naplandgames.com/agk). You can also reference the AGKHelper.java there to sort of see what needs ot be commented out. It might be easier to do it with a clean/build and manually resolve the errors though.
I do question their claim though. How do users know that it is included, but not used? Who would notice that?