Jojsticken is a program that maps keypresses on your gamepad/joypad/joystick to keypresses on a keyboard. Since it uses java (and SDL), it is cross-platform compatible and will work on every platform with support for java and sdljava (the SDL bindings).
What does that mean? Well, it means that whatever buttons you feel are useful to get access to on you keyboard - you can now get access to from your gamepad.You could use it for:
And yes, this is basically the same software as rejoystick. I'm actually the author for that project to. Didn't the web site look similar?