As we established before, X11 on OSX 10.5 Leopard is, at least kind-of, broken.
Gladly, there are numerous community efforts to bring our tragic hero back on stage. For example, like in OSX 10.4 Tiger, it is possible to deactivate the XTerm window starting up every time you start X11. It has just become a little more complicated.
First, this is what has changed with launching X11 on Leopard (as described on boredzo.org):
In Tiger, when you launch X11, it runs
xterm(unless you comment that line out).
In Leopard, X11.app is just a launcher. All it does is run
/usr/bin/login -pf $USER /usr/X11/bin/xterm. In other words, its only purpose is to run xterm (semi-)directly, by itself--it's not the actual X11 server anymore. When
xtermstarts, launchd sees it, notices that
xtermrequires X11, and launches the real X11 server (
defaults write org.x.X11_launcher app_to_run /usr/X11/bin/xlsclients
xlsclients, we can alternatively run
xprop (thanks, JP!). Both applications have the good habit not to do much (i.e. not to waste a lot of cycles/energy/water/CO2/whatever) and also not to open an annoying window like
Hope this helps :)