The second release of Unladen Swallow was made available yesterday. The project plan describes the goals as follows:
We want to make Python faster, but we also want to make it easy for large, well-established applications to switch to Unladen Swallow.
- Produce a version of Python at least 5x faster than CPython.
- Python application performance should be stable.
- Maintain source-level compatibility with CPython applications.
- Maintain source-level compatibility with CPython extension modules.
- We do not want to maintain a Python implementation forever; we view our work as a branch, not a fork.