(The answer is ad revenue, which cratered across the entire internet in February to just 25% of 2019’s average.
BoingBoing is, as far as I can understand, a jointly owned venture by the authors.
Jason acts as the publisher/frontman, who inks licensing deals. Branded product advertisements now make up a solid chunk of revenue in the media industry and with BoingBoing’s high SEO rank, probably account for the bulk of site income.)