VPPlugin.h) along with example code can be downloaded here:
Important Implementation Note: The Python interpreter is global to the VoodooPad process, and you should always perform actions on the main thread. You should also take care with global variables, since they will be seen between documents. If you don't know what that means, then don't worry about it.
Plausible Labs makes no promises that this will always stay this way. There are obvious advantage to using the same interpreter throughout a document's lifetime.