It really really depends on what you mean by global state here. If you mean the global state within the interpreter that's one thing. Preserving the global stat

It really really depends on what you mean by global state here. If you mean the global state within the interpreter that's one thing. Preserving the global state of your application is another. But a weird "global state" (really more a global property) is the semantics between concurrent pieces of code and the expectations about things like setting variables, possibly interleavings etc. The nice part of different interpreters isn't just getting around the gil, and maintaining similar isolation, but it's almost like a Terms and Services agreement: I opened this can of worms and it's my responsibility to learn what the consequences are.