Some context about this here: https://arstechnica.com/information-technology/2023/08/openai-details-how-to-keep-chatgpt-from-gobbling-up-website-data/
the robots.txt would be updated with this entry
User-agent: GPTBot
Disallow: /
Obviously this is meaningless against non-openai scrapers or anyone who just doesn't give a shit.
That won't stop OpenAI. We need actual blocking, on the server side. Problem is, with federation and all, it will be really, really difficult to do. And expensive.