I tried that build once before. I downloaded it and tried it again.
Launching it on the retina display with "useOpenGL" set to "true" had the same problem--the game window opened at the expected size, but the game graphics only take upthe lower left part of the window. If I set opengl to false, or launch the game on the non-retina display, the game graphics fill the window as expected. This is less than ideal because the game runs quicker when opengl is set to true--specifically, battlescape animations like walking characters runs faster.
I also noted that in the battlescape, when an xcom agent can see an alien, the little number button is a different color. I'm used to the number button having a red background, but it's green. That may be a deliberate change.