Ansible Tower 3.8.3 - trial licence request

Actually I am trying to use this http://releases.ansible.com/ansible-tower/setup/ansible-tower-setup-${ANSIBLE_TOWER_VER}.tar.gz

After it starts there is a screen (see in attachement) where I have to upload a license file. I am looking for this license file (trial). I still cannot find anywhere.

This way is important for us because our client uses ansible tower 3.8.3.
We have to integrate with their Tower and call its REST API. This is why we are trying to prepare a test environment.

Request licence is redirecting to this: https://www.redhat.com/en/technologies/management/ansible/try-it

But this enforce a new install which is not possible. I only need that licence file that should be uploaded to the Tower.