Further to my original post, CyberGhost has just released another 5,000 keys.
If you get an error when registering, try the tips in this comment,
CyberGhost offers a 1-Year Special Edition License for Windows, Mac, iOS, and Android FREE when you sign up via its German site.
Simply type your email address in the grey box then click the "Registrieren" button. You'll instantly receive an email with a confirmation link (check junk mail). Click on the link for the activation key. Confirm your email address right away, or you may miss out.
Includes unlimited data volume and bandwidth. The key must be activated by October 12. Deal ends September 23, or when keys run out.