I would strongly recommend docker.io from Ubuntu/Debian repos. This will be always Apache 2.0 licensed. (It's a fork of Moby packaged by Debian people).
Docker Engine looks problematic since the license isn't clear at all. For instance, Microsoft didn't include Docker into GitHub Actions, they also forked Moby and packaged it on their own, since they can't comply with the End User Agreement of Docker Engine.
No, you can apt-get docker.io (the repackaged version available for the last 2-3 LTS releases, built from source and with fan networking support). Works for 99.9% of your use cases.
