Hi Phil,
OK - I've had a quick look at the MS Docs - this is the advice on MS official website:
"
Who can I share my Microsoft 365 Family subscription with?
You can share your subscription benefits with up to five other people, (total of 6 people using your subscription). These people can be
inside or outside of your family group, and each person can install Office on all their devices and be signed in to Office on five devices at the same time."
Learn more about sharing your Microsoft 365 Family subscription - Office Support
However, as you would expect, the other people should trust you; the owner of the subscription has control over allocating & revoking the subscription, and the software will stop working if subscription is revoked.
However the owner can't access any information from others within the subscription (e.g. they can't see contents of someone else's OneDrive or read other people's email). i.e. they are not a superuser or systems admin, just a licensing allocator.