Renderer.receiveShadows  

// make the object not receive shadows

renderer.receiveShadows = false;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void Awake() {
renderer.receiveShadows = false;
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def Awake():
renderer.receiveShadows = false