Official tech helper in the discord here.
From what I understand, the biggest problem the game has with Windows Defender is that it is an unlicensed .exe file, which Windows just intrinsically doesn't trust. We can't do anything about that; to get it licensed would cost a pretty decent amount of money.
In addition to that, we have an update button within the game, which will download an update from the internet to replace files within the game. This looks a lot like trojan behavior to an antivirus, but in reality it isn't a threat.
I will reiterate that our update was not what started triggering the antivirus. The game was fine for days after the Clangen update before Windows started freaking out about it.
As sprout said, the game is open source; all the code is on Github (github link is further up on this page). You can scan through it if you want to be really sure that what you're downloading isn't a virus.
If you don't want to get the game, that's okay. But you must understand that the current situation is out of our control.