Yes, you can communicate to a slc5/04 via DH+, this is done regularly. You'll just need the correct drivers (RSLinx OEM, for example)
And to answer one of the questions from your original post, NO, a program created using RSlogix500 cannot be opened by RSlogix5000. RSLogix is for the SLC 500 family; RSLogix5000 is for ControlLogix/CompactLogix.