itch.io

I haven't installed it on android but it does say the same thing on my device! I'd assume your device just doesn't register it as an actual game. I'm pretty confident it's safe.

The game is fine I've had it installed on my samsung galaxy for months you have nothing to fear my friend

Edit: I have it on android and have had it for months 

Android just does that, so does Windows! It's a saftey measure, it's just telling you to make sure it's safe before you install it.