They are distributing for free. For free, they are distributing a compiled version of the game which I have no source to, and no license to creative derivative works of, or to perform or display publicly, and so on.
That thing, which they call Dogwalk, and are distributing for free, is clearly not open source.
The other thing, which they probably also call dogwalk, and they'll give you if you pay them presumably is open source (or maybe the more accurate term is "free software" since the source isn't publicly available - i.e. open), but that doesn't make the download on the page linked by HN open source.
That thing, which they call Dogwalk, and are distributing for free, is clearly not open source.
The other thing, which they probably also call dogwalk, and they'll give you if you pay them presumably is open source (or maybe the more accurate term is "free software" since the source isn't publicly available - i.e. open), but that doesn't make the download on the page linked by HN open source.