Yeah, but there's no release of docker daemon for mac or windows. You have to run a linux VM and install and use it there. Docker desktop basically wraps that VM process up into a little gui app. If you're willing to do it yourself then yeah a simple virtualbox VM can run docker without issues or license fees.
From what I read, the "Personal" $0 tier still has "small businesses" listed, and the little info tooltip for Docker Desktop also explicitly mentions "small businesses."
This can be found at the very bottom of that page:
> Docker Desktop can be used for free as part of a Docker Personal subscription for: small companies (fewer than 250 employees AND less than $10 million in annual revenue), personal use, education, and non-commercial open source projects.
This changed in the last year, previously docker was free to use personally or at non enterprise scale work/office.