What is the “size” of the API implementation?
It’s hard to impossible to find out. Currently the API implementation is just a wrapper to a core API for the most parts. Only newer components directly implement the API. Thus, there is really not much point in finding out how much code implements the API – and it even makes less sense in the future. Depending on the perspective, we probably can say: The whole OpenOffice.org is an implementation of the API, especially because more and more features are using the API of other components for integration.