I have not seen the video, but I read the description in the comments.
My concern with this scenario is that cat fountains get slimy pretty fast (definitely within a week). If not intended as a drinking fountain, the parts are likely not easy to clean (ridges and pores for bacteria to grow in).
Additionally, since it's unlikely that food-safe plastics were used, they may leach heavy metals (commonly found in bright colored paint) into the water.
I can't think of any concerns with the motor. A motor used in a water toy should be adequately sealed from the water to prevent shocks. If it leaked oil or other fluids into the water tank, it wouldn't last very long (unless there was a method/instructions on how to replenish these fluids, which seems unlikely).
We cannot say definitively whether this is safe or not (the videographer may have made this tank specially to be a water fountain and used the proper materials!), but it seems in general to be a bad idea.
If your cat is not drinking enough, the best method to increase their hydration is to encourage them to eat wet food. After that, consider adding a cat water fountain that is easy to clean (cats don't like gross water).