I loaded jhrp1_01.box and in the info window it states "This package is likely meant for heretic-ext."
It said the same thing when I tested out jhrp+psy-20100928.pk3 - which did seem to work pretty well but there were loads of errors in the log file and the hellstaff doesn't work so I figured I would try some other packs.
I've never heard of heretic-ext though. I have the original game heretic.wad and heretic12.wad but if there is something additional I should have then I definitely want to know! I thought those were the only 2 and that nothing more had been done with the original game.
Thanks in advance!