That's a fair point. Still, I think it's also worth acknowledging that getting paid to develop open-source software can often be more difficult than getting paid for proprietary work. According to Tidelift State of Open Source Maintainer report, 44 % of FOSS maintainers aren't getting paid for their work but would like to. Interestingly, 36 % of FOSS maintainers are getting some monetary compensation.¹
(I'm responding mostly because I found that survey. Interesting numbers.)
¹ I thought this number would be smaller. Alas, I am a pessimist.
