I think the biggest edge Tesla has is 3 + million vehicles driving around collecting data around the world with the cars equipped with the hardware for fsd.
Someone made a good point about shadow mode. It allows Tesla to get telematics, kinematics, etc from vehicles not using any software upgrades. This data will keep them so far ahead. As we have seen on this thread, the phrase "second place will need a telescope " might be an understatement
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Edit: even if any company had some of Tesla's code, they don't have millions of cars driving everyday to compile the data, let alone do something useful with said data.