RPython is a restricted subset of python indeed, but its purpose is to be a toolkit for implementing virtual machines. It is not and does not aim to be a general-purpose programming environment.
PyPy is a JITed Python runtime implemented in RPython.
The relation between PyPy and RPython is more or less the relation between CPython and C.
That line made me feel warm and fuzzy inside. He also mentionned mypy which i thought was a one man lonesome soon to be abandonned ( but absolutely fantastic) project.
