Ask HN: Is it legal/ethical trying to replicate an Udacity's autograder?

One of the training courses I really enjoyed the most is one related to Mathematics, provided by Udacity some years ago.

I've noticed people are unable to enroll anymore to these courses, e.g. https://www.udacity.com/course/ma006

The training material is still available at YouTube (Published by Udacity): https://www.youtube.com/playlist?list=PLAwxTw4SYaPlSLRIPSeloeFkkwEnnl6d4

In my opinion, receiving immediate feedback about how you did over an exercise/problem is of tremendous help while learning.

So I proposed myself to replicate the auto grader for the exercises related to the aforementioned Algebra course by means of a web application, embedding the video and showing the related questions, like it used to be when the course was alive. Still, I don't want to get into trouble, since I acknowledge the content is intellectual property.

Is it legal/ethical embarking in such a task?

Thanks!

-- Caleb