I agree that Pitchford is a dick, but I sincerely disagree about the art style comments: I don’t think it’s morally correct to “copyright” (or, reworded: claim exclusivity of) art styles, especially in this context.
I think the two works are completely independent, and Gearbox being inspired by the short film is completely appropriate.
Anything else would be no different (in my opinion) than cases like Roger Dean (the cover artist for Yes’ early albums) suing James Cameron for the floating islands in Avatar.
It’s not stealing to be inspired by someone else.
I’ve been trying OnlyOffice recently - seems pretty nice so far.