I'm afraid the download is just a .tgz file. Maybe I should take a look at this itch app. ;)
Hmmm, strange. Did it used to be packed in a zip file? Because previous versions worked fine in the app, but now it complains that there's no handler for the .tgz format when installing, even with 0.90, which I had previously installed from the app but no longer can since it's also a .tgz file in the current downloads. Installing the Windows .zip file works fine from the Windows itch app, by the way.
Of course, I can just download from the browser and it works fine, but the itch app is a nice way to install software and keep it updated when it works.