When the project has been released to the End Customer (see here), then he may login using the 'initial user password' that has been provided by the Admin. The first time the End Customer logs in, he is requested to change his password.
By doing that, the Admin's access is revoked and only the End Customer can access the installation.
Once the End Customer logs into the ETS Inside project, he can immediately verify that the Admin's access is revoked by looking at the 'Admin access' buttons.
From now on, the End Customer is able to make changes in the project.