[_delirium]

I believe he was employed by the Open Source Initiative (which he co-founded) for some years, as its President. So indirectly funded by the companies that donated to OSI.

[hollerith]

Many years after found the Open Source Initiative, ESR stated publicly that he never made any money from it, and having read most of his writings from that period and a lot of commentary on the organization, I find that statement credible.

Also, he has claimed at least a couple of times over the years that he was (at the time of the claim) a consulting programmer.