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Some extensions do release GIL while doing its own parallel processing, so, to a degree, yes.

I don't know the specifics of Python's C interfaces, but I know Ruby by default will cover all 3rd party extensions in the GIL for safety and you can release it upon entry into the extension using the C api. But doing so can be very dangerous if you're calling back into the Ruby core as you could inadvertently cause problems that the GIL was meant to protect you from.

I imagine Python works roughly the same.

Yes. Numpy releases the GIL for its array operations.

Parallelism is possible, but only for computations in native code.

FWIW Node.js is essentially the same situation.

Node got background workers recently.

Otherwise yes, Node or Ruby play by the same global lock rules.

Same in Python, except multiprocessing has actually been around for longer.

Launching multiple processes without mutable shared memory is always an option.