It looks like the Mojo compiler/runtime hooks into the CPython interpreter.
> We utilize CPython to run all existing Python3 code “out of the box” without modification and use its runtime, unmodified, for full compatibility with the entire ecosystem. Running code this way will get no benefit from Mojo, but the sheer existence and availability of this ecosystem will rapidly accelerate the bring-up of Mojo, and leverage the fact that Python is really great for high level programming already.
> We utilize CPython to run all existing Python3 code “out of the box” without modification and use its runtime, unmodified, for full compatibility with the entire ecosystem. Running code this way will get no benefit from Mojo, but the sheer existence and availability of this ecosystem will rapidly accelerate the bring-up of Mojo, and leverage the fact that Python is really great for high level programming already.
https://docs.modular.com/mojo/why-mojo.html#how-compatible-i...