What? Docker is still completely open source apart from the desktop GUI. The engine and (I'm pretty sure) all components are completely free and if anything, they have pushed for the standardization of the container runtime. Buildkit is free, compose is free, no feature is paywalled apart from Mirantis-centric stuff (not part of docker inc)
You can absolutely bet that they would get dropped like a rock if they moved to changing the engine's license. Even the docker desktop code wasn't ever open to begin with anyways.
That's just hosting though iirc. Docker hub is very important, but it's not really part of Docker the software. As in, you could deploy your own container registry with 0 licensing issues. They just didn't want to pay the bandwidth costs anymore, though I think they walked back on that for open source images.
You can absolutely bet that they would get dropped like a rock if they moved to changing the engine's license. Even the docker desktop code wasn't ever open to begin with anyways.