That’s not the only problem, I think. It’s not an adaptation of their work, it’s a “demake” which means it uses original source files or, at best, exact recreations of that work. The other projects people are comparing this to adapted Valve’s work to make something original. This isn’t original and uses the existing name. It would be very easy for Valve to make the claim that this product could be confused as an official Valve product even if most people who are interested would know the difference or be able to tell.