Multiple definitions error with TIMER0_OVF_vect

I'm using a program (written by someone else), that uses ISR(TIMER0_OVF_vect). When I try to compile in Arduino IDE (v1.05) I get a multiple definition error because Arduino's wiring.c also uses TIMER0_OVF_vect. Wiring.c isn't used by this program, but I guess Arduino checks it anyway. The author doesn't compile using the Arduino IDE, so he doesn't have to worry about this. I don't know much about interrupts and don't know anything about which one TIMER0_OVF_vect represents. How do I get rid of this error? I have a feeling it's more complex then just renaming something.

The program can be found here: https://github.com/grbl/grbl/tree/dev The specific file is stepper.c, line 419

int main() 
{
  // Your setup code goes here

  while (1) 
  {
    // Your loop code goes here
  }
}

You are now responsible for initializing everything else: timers for PWM, ADC, whatever else I can't think of right now.

[quote author=Coding Badly link=topic=243288.msg1742923#msg1742923 date=1401308966] You are now responsible for initializing everything else: timers for PWM, ADC, whatever else I can't think of right now. [/quote]

That's pretty cool. I don't know anything about initializing all this stuff, but I'm wondering if that's already being taken care of in the original program. Can you tell me if that's the case?