Copyright doesn’t protect an idea for a game (which includes genres, as an “idea”). It also doesn’t protect the ideas or systems used in developing that game.
To clarify: I was specifically commenting on what was mentioned in your original post
Since they were put next to each other, I assumed they were related. I’m now assuming that these were two separate questions, being: “Is it legal?” and “Do you like the systems/physics in the mod?”.
Normal trademark/copyright law still applies then. Copying the assets. The operator select screen would be a prime example of infringement, and characters would be referenced as being copies too (infringing on likeness).
EDIT: Legally, it’d be something that someone could pursue, and the creators probably know that. They’re probably just not worried about it, until it actually happens (if it happens). But that’s me making assumptions about their point of view.
It’s interesting to see a fan-made recreation of it but unless they got permission then Ubisoft could take legal action against it if they wanted to. I’m hoping that operator select screen was just Photoshop and not what’d actually be used. If they incorporate that specific image in it then they’d definitely be setting themselves up in a bad position.
I’m friends with the owner and thinking of the legal reprecautions if this ever made a penny of profit makes me regret posting this or thinking about it. But welp-
I think a solution might be to dub it a “roleplay” to try going through a loophole that’s often used by many other servers (like in Gmod) to do things like replicate Star Wars.
I might be wrong but if anyone can research like a lawyer into it- that’d be great.