I'm not sure what's going on with the OSX version, but I updated the browser version so you should be able to play that one now.
I managed to make the download work (for anyone with the same issue: you need to allow apps made by anyone to open, not just apple/trusted sources), but the browser is also working now, thank you! It's a lovely little game, it's been in my bookmarks for years but only now did I see it was available for mac too.