Mypy source code is available on GitHub:
https://github.com/JukkaL/mypy
Clone the repo and give it a try! Currently the mypy implementation lets you mix static types and dynamic types and translate mypy programs to readable Python. Type annotations and casts are treated as comments when translating to Python. As such there is no performance boost yet. The current prototype supports a useful but somewhat limited subset of Python features (library support is still limited).
There is also an issue tracker for reporting bugs.
