Terrorists would have a field day if they had access to nuclear weapons. The only thing stopping them is that the barrier to independently developing nuclear weapons is so high that it's only practical for powerful nation-states to have them.

In comparison it's trivial for both terrorists and powerful nation-states to download 60GB of weights and crunch numbers on a GPU cluster. Arguably the hardware requirements of the most sophisticated LLMs act as a similar barrier to widespread adoption even if they were open-source, but to nowhere near the same extent, and as with nukes that's just a happy coincidence of the current state of technology/known physical limitations than an intentional barrier to stopping their spread. Even as we speak there has been collective interest in discovering a way to decrease those hardware requirements (INT8/INT4 quantization) as much as possible so more people can run them for themselves, which shows no signs of abating.

All I can say is we're lucky that physics prevents us from mass-producing ICBMs on a fast enough time schedule, because if it were possible we'd probably attempt to do so for the sake of trying.