One other potential difficulty is that Jython doesn't aim to be 100% compatible with existing C extensions. Unladen swallow does. Plus, I believe Unladen Swal

One other potential difficulty is that Jython doesn't aim to be 100% compatible with existing C extensions. Unladen swallow does. Plus, I believe Unladen Swallow is essentially a branch of the CPython source code while Jython was written from scratch.