PS: since you have a subscription for Kopano One the recommended approach to get support is to directly open a ticket with the Kopano helpdesk. This place is just a forum for the community and not an official support channel.
similar to how it is with our general release (the packages that you were referring to are the nightly builds), the packages of Kopano One can only be fully used by Kopano customers with a valid subscription.
You can install the software without a valid subscription but the server will prevent you from creating users until a license file has been supplied.
What happens if the subscription to kopano one runs out?
Its clear that there won’t be any updates - but will it stay usable at the current state?
You can easily simulate what happens when you remove your license key and restart the kustomerd process (a restart may not be necessary as the service was afaik design to detect changes license files directly).
And the hard version
deactivate the autostart customer service
(systemctl disable kopano-kustomerd.service)
reboot the server and open the web app
No more work possible;)