That's only because it's not an established publisher. It's just an indie game. Most games on itch.io will be flagged like that lol.
You don't need to download the game if you don't want. But it is not a virus. It's only saying that because it's a game from an unknown publisher. Usually most antivirus software is going to flag any file that comes from an unknown source without verification. But this game has over 5,000 downloads total and I don't have 5,000 people complaining about viruses, so it must be a safe file. Just look up how many guys played this game on YouTube already. They are all fine lol.