You are correct that there is no legal way to download MATLAB and use it indefinitely for free on your own (no affiliations). Python or Octave could be an alternative depending on your application.
Weird, when i create my acount and click in MATLAB, it doesn't show as it was in the video, there is a button to sign in, and every time i click in it the page refreshes
Yeah I wish it were “more free”. The free 10hrs of MATLAB online was a surprising release for a pay-to-use-software. Unfortunately, MathWorks is a for-profit entity and I doubt it’ll ever truly be free unless they adopt a different revenue model. There’s always Python ;)