Can I download and use this mod?

No. Downloading and using this mod without an extra license agreement is a violation of the license agreement.
The extra license agreement is granted if you have received an invitation.

Can I receive an invitation?

You will get an invitation when the time is right.

Why is this mod public?

Because I not have the possibility to make it private.

Why is this mod on the mod portal?

Because there is no possibility to choose another portal in the game.