The only way to use Google Charts now outside of Google is via the dynamically loaded library. We're working on open-sourcing a subset of the library, which you would be able to compile as a module into your code. No idea when that will become available.
Unfortunately, even that subset will not be usable along with the rest of the dynamically loaded library, though maybe this will be possible if we release a version that loads the same module dynamically. Why bother? If we do this right, you might be able to substitute modified versions of the same module.