To run a ZEO server, you'll need Python 1.5.2 or 2.0, and the ZODB packages from http://www.amk.ca/files/zodb/have to be installed.
Note for Python 1.5.2 users: ZEO requires updated versions of the asyncore.py and asynchat.py modules that are included in 1.5.2's standard library. Current versions of the ZODB distribution install private versions of these modules, so you shouldn't need to grab updated versions yourself. (The symptom of this problem is a traceback on attempting to run a ZEO client program: the traceback is ``TypeError: too many arguments; expected 2, got 3'' around line 100 of smac.py.