The article I read explains this well:
Now through December 31st, you can stream all classes featured at the Nikon School Online. Normally, these classes cost between US$15 and US$50 each. Each course is taught by a professional photographer and features in-depth lessons to improve your photo-taking skills.
However, it is important to note that although it is called the “Nikon School Online,” you do not need to own a Nikon camera to take advantage of these free courses. A few classes focus on Nikon-specific gear, but most of the classes available focus on photography as a skill set and how to improve.
You will need to sign up and provide your name and an email address before you can watch. But don’t worry; you can opt-out of receiving marketing emails after signing up.
"Update: I can't find where to subscribe, they seem to just have instant videos on the page I provided."
It's because you are already logged in I think.There was a link on the page saying "if you want to see the full length video, click here". And it's a link to subscribe.