Does the Laser DL445 use the same port on the STEPCRAFT as the 3D Printer and HF500 spindle?

Yes, they both use the same serial port on the back of the machine.  You would need to disconnect the cable and reconnect the attachment that you wish to use.  STEPCRAFT also offers a Switchbox which allows you to connect everything and simply turn the dial to select the attachment you wish to use.  This is very handy if you are constantly changing attachments.