Well, not quite it seems. The version I was using is 8.14, which is about 6 years later than your 5.5. It needs exactly the same hack as the earlier one, though: it must be in "/boot/apps". It has an elaborate Install script, which of course no longer works.
I've done a short comparison of that one and the 5.5 I downloaded from you, and they seem to behave pretty much the same. Some stuff -- like the 'tiger.ps' example -- renders very nicely, but for some unknown, and annoying, reason, all text is rendered negative (white on black)! This doesn't happen with the same code on BeOS, where everything renders properly.
If anyone wants to play with the 8.14 version, I've put it on BeShare [currently sitting with AGMS, as TyCom is majorly down ATM]. Two files: Ghostscript-8.14-1-x86.zip, and ghostscript-fonts-std-8.11.tar.gz
Things get murkier, though, as I also discovered on my old partition a "Ghostscript_Haiku-2013_02_25.zip" that I don't seem to have been using. I see the 'share folder installed with all its stuff, and the libraries from the zip (including 'libcairo') in common/lib, but none of the executables are installed, so I must have removed them. No memory of what the problem was, but obviously I preferred the older one. Anyone have any clue?
It would be nice to have a good Ghostscript port. I was thinking it might make a good GSoC project, but the thought is a bit late...