Just figured out that when you put a price tag for your game it says to pay "$__ or MORE." I think the creator thought they would also make the web version paid? I don't really know.
If you look closley, if you wanna download, lets say the dmg file, it says "if you pay 1$ USD or more." The reason why it appeard as an optional donation is probably to make it so you can pay extra if you want to donate.
I sure hope it does :3 Also the only reason I found this was because I was looking a projects made with scratch, because I am also making a project with scratch, no mods like turbowarp or penguinmod ;)