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He used FREE assets of a game kit of unity to learn game design without changing anyhing but the name, literally just repackage and rename https://learn.unity.com/project/2d-game-kit-2 same for Alien Earth 2 with a game kit called "The Explorer" https://learn.unity.com/project/3d-game-kit

I created new levels, secret locations and new enemies!

Unity can get you for copyright infringement

(-1)

they technically can't get him for this since it's an asset and since he got it of the asset store he can do with it as he please as long as he doesn't package the asset and put it up for sale. him releasing it as a game  means his not breaking any roles and as shity as  it looks to just release something people worked on as your own his not breaking any rules 

(+1)

Yes they can cause it's their asset kit, there is no licensing that says he can monetize this in anyway. Look at the licensing terms.