Cornerstone is still in active development and should NOT be use in any production system. The structure and code quality is not ready for dependable maintainable releases.
Cornerstone still needs lots of testing and validation before releasing. The framework is also is very active development (heavy churn). Apis will come and go, even complete classes may move, be refactored, or even deleted.
Cornerstone in as development framework to help speed up and make building applications and systems much easier.