Another benefit to Universities is that they have some of the oldest, most culturally focused DNS zones. EDU is the most likely of just about any root TLD today to avoid succumbing to for-profit pressure and is one of the stablest managed TLDs, so an address on an EDU domain perhaps has the highest likelihood of not changing deep into the future (assuming properly managed by the University itself). (There's still signs that ICANN itself can be bought and redelegate EDU at which point all bets are off.)
It might not even take that big of an Endowment to get the University to do something like that. Universities are pretty good at Endowment (Annuity) math (because they have to be), University web hosting is still relatively cheap (easy access to low cost labor from "passionate" students, a DNS TLD that mostly can't just raise prices for arbitrary profit reasons) and no signs that it wouldn't be so in perpetuity. (Just keeping mind the risks of data loss of cheap labor.)
A quick search didn't find me an Annuity calculator that can calculate past 100 years (and I don't have the Excel fu to do it by hand because I'm not an accountant), but just experimenting with some numbers: let's say $25/month covers expected hosting costs and a tiny bit of funds for other web needs (maybe a pizza allowance for students) to cover that $25/month for a full century at a somewhat low expected annual growth rate of 1% you only need to start with at least $19k endowment today to cover the annuity. You probably don't want to start that small for sociopolitical reasons (to give them more reasons to abide by the terms of the annuity for the full length of it), but on the flipside you probably don't need anything at all close to a $1B dollars to do such a thing either.
It might not even take that big of an Endowment to get the University to do something like that. Universities are pretty good at Endowment (Annuity) math (because they have to be), University web hosting is still relatively cheap (easy access to low cost labor from "passionate" students, a DNS TLD that mostly can't just raise prices for arbitrary profit reasons) and no signs that it wouldn't be so in perpetuity. (Just keeping mind the risks of data loss of cheap labor.)
A quick search didn't find me an Annuity calculator that can calculate past 100 years (and I don't have the Excel fu to do it by hand because I'm not an accountant), but just experimenting with some numbers: let's say $25/month covers expected hosting costs and a tiny bit of funds for other web needs (maybe a pizza allowance for students) to cover that $25/month for a full century at a somewhat low expected annual growth rate of 1% you only need to start with at least $19k endowment today to cover the annuity. You probably don't want to start that small for sociopolitical reasons (to give them more reasons to abide by the terms of the annuity for the full length of it), but on the flipside you probably don't need anything at all close to a $1B dollars to do such a thing either.