> Are similar mitigations also needed in the VMs for other dynamic languages, such as CPython/PyPy, Ruby MRI and Lua/LuaJIT?
Yes.
> What about the JVM and Microsoft's CLR?
Yes.
Yes.
> What about the JVM and Microsoft's CLR?
Yes.
As for implementations of Python and Ruby, they might not worry about these attacks - because AFAIK they do not try to support secure execution of untrusted code.