First link has a typo (an errant á), should be: https://krita.org/en/item/funding-kritas-development/ .. however it's even older (from 2016)
Their windows store buy page[0] (also from 2017) suggests they'd prefer you donate than buy.. so it's probably not a viable model.
[0]: https://krita.org/en/item/krita-available-from-the-windows-s...