Yes, or there should be a ROBOTS.TXT file that describes how the code in a directory may be indexed or used by machines (e.g. malware scanning okay, no LLM trai

Yes, or there should be a ROBOTS.TXT file that describes how the code in a directory may be indexed or used by machines (e.g. malware scanning okay, no LLM training, etc.) But you're probably correct that such rights should just be covered by the license itself. Your reciprocity suggestion could also work, since it would mean any LLM trained on even a single file of GPL code would be "poisoned" in the sense that any code it produced would also be GPL. This would make people wary of using the LLM for writing code, and thus would make the creators of it wary of training it on the code.