RHEL licensing requirements when using Docker vs. VirtualBox

Can you verify if my understanding below is correct?

Since docker containers share the kernel, it seems that all docker containers, running on the same machine, could share the same Red Hat license/registration.

On the other hand, if I run multiple VirtualBox instances (each built to run RHEL7), seems that each instance would need to have a license/registration (it may be the same on more than one instance, but then these instances could not be run concurrently). Also, it seems that the same license could not be shared by the underlying OS and the VirtualBox instances that run in it.

Is my understanding correct/faulty?

Notes:
The machine, on which the docker containers or VirtualBox instances will run, has a Red Hat Developer license.
This machine's OS is RHEL7.