As you probably have seen this on the Sonus Paradisi site :
"The samples [for Freiberg] are encrypted and dongle protected. Hauptwerk version 5 or higher required for use." and "Freiberg DEMO (Surround, HW5 only)."
The available versions don't work on HW 4.2.
You may find some of the organs on https://piotrgrabowski.pl/instruments/ will work on HW 4.2 (for example the Strassburg set.
You may also find that some of the organs at Pipeloops such as http://www.pipeloops.com//product_info.php?cPath=24&products_id=41 may meet your needs.
You could, of course upgrade to Hw 6!
Iain