Follow these instructions to make it work on Mac:
Right click on the app icon> Show package contents> Contents folder
Rename the exec file "MacOS" to "powder-x" (it will ask for your computer password)
Create a new folder in the same place as the exec file, name it "MacOS" (it may ask for password again)
Move the powder-x file to the MacOS folder (it will ask you to authenticate)
Go back and right click on the app icon> Open (hit ok to open)
Also on an unrelated note,
Is the change for the shape of the circle brush expected to be permanent? I think the smooth shape has some major flaws because it looks less like a circle than it did before. Without the 4 points, the sides of the "circle" are too flat, especially for circles with diameter <13px. This essentially makes it a square with rounded off corners. Using shift to make an oval exaggerates this issue. Large circles do look better with the sides smoothed off, but at least for sizes <13, I would strongly prefer the vanilla brush shape. At 3px, its the same as a square so it is even more redundant.