This actually works but after you're done playing you'll have to disconnect the joystick. Found it on the vega strike page.
Download and install this:
http://www.apple.com/downloads/macosx/games/utilities/gamepadcompanion.html
It's a key mapper for the joystick. Select your joystick on the left, for Y-axis push joystick up and when it asks you, use the up arrow on the screen. You'll have to map all the keys and you may want to turn the sensitivity down but this really works for me.
Download and install this:
http://www.apple.com/downloads/macosx/games/utilities/gamepadcompanion.html
It's a key mapper for the joystick. Select your joystick on the left, for Y-axis push joystick up and when it asks you, use the up arrow on the screen. You'll have to map all the keys and you may want to turn the sensitivity down but this really works for me.