Soon (end of May, according to the current roadmap) this feature will also be available with the Docker Engine (so not only as part of Docker Desktop).
As a reminder, Docker Engine is the Community Edition, Open Source and free for everyone.
This comment kind of makes it sound like maybe you can run Docker Engine directly on these operating systems (MacOS, Windows, etc.), is that the case?
You were always able to manually install Docker CE within WSL2 on Windows. But if you want to have an integrated Docker experience on the Windows host, you need to use Docker Desktop, which will ship it's own Linux VM and performs the transparent integration with the Windows host.
This is fully independent of the Docker Model Runner feature thought :)