I'm not sure whether I understand the legal terms of Docker regarding its use on virtual machines.
As far as I understand it, Docker's general license limitations do not allow to use Docker on virtual machines without a (rather expensive) business license.
Since Plone's main installation strategy relies on containers, those license limitations are relevant for the Plone community and might lead to consider including additional intallation strategies for Plone.
4.1 General License Limitations.
...
(b) Under the terms of this license, you shall not, and shall not encourage any third party to: [...]
[...]
(vii) use the Service on virtual machines without a license to Docker business for such use; [...]
Service beeing defined as follows:
1. Definitions
[...] "Docker Subscription Service” or the “Service” refers to the applications, software (including any Open Source Software), products and services provided by Docker, including any beta or trial versions.
As far as I understand, 4.2 (Specific License Limitations – Docker Desktop) adds further restrictions to the Docker Desktop component of the Service at the level of the Personal Offering without overriding 4.1 (General License Limitations).
Docker can shout whatever they want, I don't believe it applies to running the containers.
The docker engine stuff is licensed as open source: Docker Engine overview
Please contact Docker directly to make sure what is what. Don't wait for their community forums plus when you have an answer please post it to said forums and this.