If you have an Enterprise Edition license (basically if you are one of our customers), you can just enter the license file in the UI.
If you want to use the Free Edition or a trial of the Enterprise Edition, your browser (Chrome or Firefox) must have access to the internet so that you can create a Dataiku account (that will generate a licence file for you).
In any case, on a Linux server, you can install DSS and the dependencies without internet. See the doc: https://doc.dataiku.com/dss/latest/installation/new_instance.html#manual-dependency-installation
Jeremy, Product Manager at Dataiku