itch.io

Well, yes but actually no.

The game is continued on Steam under the name "Warbox". "Warbox: Sandbox Warfare" is an entirely different game. Similar mechanics (a shooter simulator) but not made by the same guy.

Best thing you can do is to wishlist it. Once it goes on sale/has a discount, Steam will send you an email to notify you about it.

That's because it isn't tagged by the devs which platform the game is supported on (Windows, Mac, Linux). If there isn't a tag for which platform it's on, the app cannot download it.