I think this might be what they mean: Has anyone explored the idea of funding UBI with bequests?

Similar to how a university builds up an endowment via donations, and that endowment funds the day to day operations of the university, we could start a "UBI endowment" and encourage people to leave money to it when they pass. It would pay out very little at first, but over time think (50-100 years) we might accumulate enough wealth in the endowment to provide a healthy basic income.

Income accrues to the owners of capital. Currently, the world's capital is held very unevenly. Over time, humanity as a whole should become the owners and beneficiaries of its capital. Bequests to a UBI endowment could be a fairly apolitical, non-radical, non-disruptive way to slowly make this important transition.

Source: https://www.reddit.com/r/BasicIncome/comments/6lnumz/funding...