Turns out that VPS provider Vultr's terms of service were quietly changed some time ago to give them a "perpetual, irrevocable" license to use content hosted there in any way, including modifying it and commercializing it "for purposes of providing the Services to you."
This is very similar to changes that Github made to their TOS in 2017. Since then, Github has been rebranded as "The world’s leading AI-powered developer platform". The language in their TOS now clearly lets them use content stored in Github for training AI. (Probably this is their second line of defense if the current attempt to legitimise copyright laundering via generative AI fails.)
Vultr is currently in damage control mode, accusing their concerned customers of spreading "conspiracy theories" (-- founder David Aninowsky) and updating the TOS to remove some of the problem language. Although it still allows them to "make derivative works", so could still allow their AI division to scrape VPS images for training data.
Vultr claims this was the legalese version of technical debt, that it only ever applied to posts in a forum (not supported by the actual TOS language) and basically that they and their lawyers are incompetant but not malicious.
Maybe they are indeed incompetant. But even if I give them the benefit of the doubt, I expect that many other VPS providers, especially ones targeting non-corporate customers, are watching this closely. If Vultr is not significantly harmed by customers jumping ship, if the latest TOS change is accepted as good enough, then other VPS providers will know that they can try this TOS trick too. If Vultr's AI division does well, others will wonder to what extent it is due to having all this juicy training data.
For small self-hosters, this seems like a good time to make sure you're using a VPS provider you can actually trust to not be eyeing your disk image and salivating at the thought of stripmining it for decades of emails. Probably also worth thinking about moving to bare metal hardware, perhaps hosted at home.
I wonder if this will finally make it worthwhile to mess around with VPS TPMs?