While this is generally true, Wikipedia content is explicitly licensed with a pretty permissive license.

Eyeballing the english-language summary, the only thing that seems to be tripping GenAI is the “don’t hurt us” section about causing harm to their servers, which explains the story here.

If LLM.comapnies wanted to just put up with a delay due to how often Wikipedia lets you download everything, they’d probably be able to just do that.