To put that into perspective of what it means, conservatively they can spend $2.14B every year and never touch the principle of their $53.6B[1] endowment following the "4% rule".
They already fund a fraction (1/3, I think) of their annual operating budget (>$6B) doing something similar to that. Ah, the article you linked says more or less that.
IIUC, The controversy was that some folks wanted to draw down the principal to do capital improvements (new buildings, etc) and other folks wanted to be as conservative as possible (potentially not even using the interest for operations).
