OK, Wikipedia uses open-source software, so one could clearly branch that. And given Creative Commons licensing, I suppose that one could clone the entire site, as the basis for an alternative. Providing attribution, and marking changes, would be somewhat hairy, but conceivably doable.
And indeed, I see that Larry Sanger has been championing a blockchain-based alternative, Everipedia.[1] Wikipedia calls it "commercial".[2] And I see that its business model relies so far on ads and sponsorship notices.
However, I gather that they didn't just clone existing Wikipedia content. But accounts are invite-only, and I don't do either Telegram or Reddit. I wonder why they didn't use Wikipedia content. Maybe they don't want to use Creative Commons licensing.
Edit: Damn, Telegram wants a mobile number, which Mirimir doesn't have. So is there another way to get an invitation to Everipedia?
0) https://creativecommons.org/licenses/by-sa/3.0/
1) https://everipedia.org/
2) https://en.wikipedia.org/wiki/Everipedia