he could invest 50% or more of his salary in this work via donation and it would probably help the cause much more than his 40 hours/week. It sounds more like a middle life crisis to me.

ymmv: if "the cause" has technical or scientific elements and you are a skilled engineer or scientist your contribution of 1000h/y work on target is significantly larger than donating $1M/y.

Yes, but you also need quality of life.

I've been in a startup where the product was so cool that we'd get people working for nothing but options because they were too burned out by $MEGACORP developer culture. The money developers were leaving was so ridiculous I figure we could have charged people to work for us and we'd still have gotten more applications than we knew what to do with.

categorical imperative: if everyone did that nobody would do the actual work. there are problems in the world that must be solved with software engineering. software engineers need to work on them, and highly skilled ones, too.

disclaimer, i guess: i work at a sister project of the NAO

He actually discusses the merits of "earning to give" vs "working to give" here: https://www.jefftk.com/p/leaving-google-joining-the-nucleic-...