A recent article by Zeynep Tufekci in Wired clued me in to this GitHub thread on core-js adding a donation request to its postinstall script: https://github.com/zloirock/core-js/issues/548
It's kind of incredible to me the amount of self-righteousness and entitlement in that thread. The real tragedy is that unpaid maintainers are doing all this work for free, and big corporations are happily exploiting it without a care in the world.