I was finally able to combine the two example sketches (BH1750 Lux sensor and the HC-SR501. I thought I would share it in case it might help out another newbie like me ;-)

/**
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * REVISION HISTORY
 *Light/Motion sensor using sketches from idefix and Henrik Ekblad
 * 
 * DESCRIPTION
 * Arduino BH1750FVI Light sensor
 * communicate using I2C Protocol
 * this library enable 2 slave device addresses
 * Main address  0x23
 * secondary address 0x5C
 * connect the sensor as follows :
 *
 *   VCC  >>> 5V
 *   Gnd  >>> Gnd
 *   ADDR >>> NC or GND  
 *   SCL  >>> A5
 *   SDA  >>> A4
 * http://www.mysensors.org/build/light
 * Motion Sensor example using HC-SR501 
 * http://www.mysensors.org/build/motion
 */


// Enable debug prints to serial monitor
#define MY_DEBUG 

// Enable and select radio type attached
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69

#include <SPI.h>
#include <MySensors.h>  
#include <BH1750.h>
#include <Wire.h>

#define CHILD_ID_LIGHT 0
#define DIGITAL_INPUT_SENSOR 3   // The digital input you attached your motion sensor.  (Only 2 and 3 generates interrupt!)
#define CHILD_ID_Motion 1   // Id of the sensor child
unsigned long SLEEP_TIME = 30000; // Sleep time between reads (in milliseconds)

BH1750 lightSensor;

// V_LIGHT_LEVEL should only be used for uncalibrated light level 0-100%.
// If your controller supports the new V_LEVEL variable, use this instead for
// transmitting LUX light level.
MyMessage msgLight(CHILD_ID_LIGHT, V_LEVEL);
// Initialize motion message:
MyMessage msgMotion(CHILD_ID_Motion, V_TRIPPED);

uint16_t lastlux;

void setup()  
{ 
  lightSensor.begin();
  pinMode(DIGITAL_INPUT_SENSOR, INPUT);      // sets the motion sensor digital pin as input
}

void presentation()  {
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Lux/Motion Sensor", "1.0");

  // Register all sensors to gateway (they will be created as child devices)
  present(CHILD_ID_LIGHT, S_LIGHT_LEVEL);
  present(CHILD_ID_Motion, S_MOTION);
}

void loop()      
{     
  uint16_t lux = lightSensor.readLightLevel();// Get Lux value
  Serial.println(lux);
  if (lux != lastlux) {
      send(msgLight.set(lux));
      lastlux = lux;
  }
  
 // Read digital motion value
  boolean tripped = digitalRead(DIGITAL_INPUT_SENSOR) == HIGH; 
        
  Serial.println(tripped);
  send(msgMotion.set(tripped?"1":"0"));  // Send tripped value to gw 

  // Sleep until interrupt comes in on motion sensor. Send update every two minute.
  sleep(digitalPinToInterrupt(DIGITAL_INPUT_SENSOR), CHANGE, SLEEP_TIME);
}

@Matt I used your code as a basis to control some 433Mhz outlets from Aldi (in Germany). The system is their "Easy Home" brand, made by Globaltronics. The model designation is GT-9000. It needed a few tweeks from your code. In case anyone else has, or will get, this package, here is the code (pay attention to the "void setup" section):

// Enable debug prints to serial monitor
#define MY_DEBUG 

// Enable and select radio type attached
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69

// Enable repeater functionality for this node
// #define MY_REPEATER_FEATURE

#include <SPI.h>
#include <MySensors.h>
#include <RCSwitch.h>

#define NUMBER_OF_PLUGS 4 // Total number of attached plugs

#define CODE_1On "110001010000001101110000"
#define CODE_1Off "110011011100000100010000"
#define CODE_2On "110001010000001101110100"
#define CODE_2Off "110011011100000100010100"
#define CODE_3On "110001010000001101111100"
#define CODE_3Off "110011011100000100011100"
#define CODE_4On "110001010000001101110010"
#define CODE_4Off "110011011100000100010010"

RCSwitch mySwitch = RCSwitch();

void setup() {
  mySwitch.enableTransmit(4);
  mySwitch.setRepeatTransmit(3);
  mySwitch.setPulseLength(510);
  mySwitch.setProtocol(5);
}

void presentation()  
{   
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("433mhz switch", "1.0");

  for (int sensor=1 ; sensor<=NUMBER_OF_PLUGS;sensor++) {
    // Register all sensors to gw (they will be created as child devices)
    present(sensor, S_LIGHT);
  }
}


void loop() 
{
}

void receive(const MyMessage &message) {
  // We only expect one type of message from controller. But we better check anyway.
  if (message.type==V_LIGHT) {
  int incomingLightState =  message.getBool(); 
  int incomingOutlet = message.sensor;
  
  Serial.print("Outlet #: ");
  Serial.println(message.sensor);
  Serial.print("Command: ");
  Serial.println(message.getBool());
 
 if (incomingOutlet==1) {
 if (incomingLightState==1) {
    // Turn on  socket 1
    Serial.println("Turn on Socket 1");
 mySwitch.send(CODE_1On); // These codes are unique to each outlet
 delay(50); 
 }
 if (incomingLightState==0)  {
    // Turn off socket 1
 Serial.println("Turn off Socket 1");
mySwitch.send(CODE_1Off);
delay(50); 
 }
 }
 if (incomingOutlet==2) {
 if (incomingLightState==1) {
    // Turn on  socket 2
    Serial.println("Turn on Socket 2");
mySwitch.send(CODE_2On);
 delay(50); 
 }
 if (incomingLightState==0)  {
    // Turn off socket 2
 Serial.println("Turn off Socket 2");
mySwitch.send(CODE_2Off);
delay(50); 
 }
 }
 if (incomingOutlet==3) {
 if (incomingLightState==1) {
    // Turn on  socket 3
    Serial.println("Turn on Socket 3");
mySwitch.send(CODE_3On);
 delay(50); 
 }
 if (incomingLightState==0)  {
    // Turn off socket 3
 Serial.println("Turn off Socket 3");
mySwitch.send(CODE_3Off);
delay(50); 
 }
 }
 if (incomingOutlet==4) {
 if (incomingLightState==1) {
    // Turn on  socket 4
    Serial.println("Turn on Socket 4");
 mySwitch.send(CODE_4On);
 delay(50); 
 }
 if (incomingLightState==0)  {
    // Turn off socket 4
 Serial.println("Turn off Socket 4");
mySwitch.send(CODE_4Off);
delay(50); 
 }
 }
  }
 delay(50);
}```