It makes sense when you consider it as 'Restricted Python' (although there is another project of the same name).

I had the exact same thought. R is a pretty high-profile language; they could even couch a name change in positive terms. They'd probably get more publicity if they weren't competing with a popular package.

Me too. Why not call it PythonC?

That could cause confusion with CPython (the main python implementation) and possibly also Cython (C extensions for Python).

RPython isn't really much like C, so that would be misleading.