I think it might work if you try to open it up using the itch.io launcher...as itch.io seems to have trouble making Mac apps executable, so the "The application can't be opened" issue happens frequently with them...I think it might be because itch.io would prefer that developers launch their applications through the itch.io app instead of by itself??
But there is also another way to get the app to work using Terminal:
First, I removed all attributes from the mac 02 windowed.app bundle by typing this command in Terminal:
xattr -cr
Then I hit the space bar once and dragged the entire mac 02 windowed.app onto the Terminal window and hit return.
Next, I typed in Terminal:
chmod 777
Hit the space bar, and then I took the app's binary, which is in mac 02 windowed.app/Contents/MacOS, and dragged it onto the Terminal window and hit return.
Then the app should launch. Hope that's helpful.