Anyway, what Linux kernel are you running? If you're using a recent kernel (2.6) or a recent RedHat/Fedora release you may be running with NPTL, a new threading library that offers 'true' threads. This ends up with all the threads being under one process instead of many.

I am running 2.4.20-31.9 Red Hat Linux release 9 (Shrike).

Just a suggestion though. Is performance OK? If it is I wouldn't worry.

And the performance is not only not ok, it's devastating.

...

after several days of running zope my linux box says:

top: 21800 zope 25 0 2212 4 0 S 1.5 0.0 6:13 0 python

ps: 21800 ? S 0:00 /home/zope/bin/python /home/zope/z2.py -Z1 -t5 -X -w8080 -M /home/zope/var/bigm.log -l /home/zope/var/event.log 21801 ? S 6:15 /home/zope/bin/python /home/zope/z2.py -Z1 -t5 -X -w8080 -M /home/zope/var/bigm.log -l /home/zope/var/event.log

Any idea why zope won't spawn more threads?

I have zope running on several servers but never had any problem like that.