I have found this:
http://library.thinkquest.org/2971/psm.txt
Hope, it will help.
By the way, I've been searched with google, and found out that, PSM is an amiga format, or something like, and there isn't fully suppert, just the one that MPTracker and some other program does. Hope, I'm wrong.
EDIT: http://www.modplug.com/
You can download here modplug tracker & player, and it's even opensource! So I think it will be possible to use the PSM files in open jazz. It seems JJ1's PSMs are working with this player. (Epic Pinball has some psms which ones didn't)