Tritium 0.3.5 from the Sourceforge download and 0.3.8 Debian package both attempt to connect to :0 even when DISPLAY is set to eg :1.0:
koisoke@kaarand:~$ export DISPLAY=:1.0 && tritium
Xlib.protocol.request.QueryExtension
/usr/bin/tritium: Screen 0 already managed by some other window manager
/usr/bin/tritium: Another window manager already running?
I am using plwm 2.6a and python-xlib 0.14.