i've edited it around a little, here's more info
SCRIPT:
#!/bin/sh
CWD="`dirname \"$0\"`"
#export PATH=./sw/bin:$PATH
#export LANG=fr
#export LC_ALL=fr_FR
export PATH=/usr/bin:/bin/:/usr/sbin:/sbin:/usr/X11R6/bin
ulimit -n 512
### Work around open-X11's problem with whitespace
display="/tmp/$USER-X11-display"
getter="/tmp/$USER-X11-getdisplay"
rm -f "$display"
cp "$CWD/sw/bin/getdisplay.sh" "$getter"
open -a X11 "$getter"
deadline=$((`date +%s` + 60))
until [ -f "$display" -a -r "$display" ]; do
if [ `date +%s` -ge "$deadline" ]; then
echo "Could not get display!"
exit 1
fi
sleep 1
done
export DISPLAY=`cat "$display"`
exec "$CWD/sw/radiant14/radiant"
APPLESETTINGS.PLIST
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Creator</key>
<string>Platypus-3.2</string>
<key>EncryptAndChecksum</key>
<false/>
<key>IsDroppable</key>
<false/>
<key>OutputType</key>
<string>None</string>
<key>RemainRunningAfterCompletion</key>
<false/>
<key>RequiresAdminPrivileges</key>
<false/>
<key>ScriptInterpreter</key>
<string>/bin/sh</string>
</dict>
</plist>
TREM.GAME
<?xml version="1.0" encoding="iso-8859-1" standalone="yes"?>
<game
name="Tremulous"
enginepath="/Users/graham/Desktop/games/Tremulous"
gametools="/Applications/MacRadiant /MacRadiant.app/Contents/Resources/sw/radiant14/trem"
basegame="base"
engine="tremulous.app"
gamename="Tremulous"
shaderpath="scripts/"
/>
CONSOLE SAYS
XFree86 Version 4.4.0 / X Window System
(protocol Version 11, revision 0, vendor release 6600)
[DRI] screen 0 installation complete
Screen 0 added: 1680x1050 @ (0,0)
error opening security policy file /usr/X11R6/lib/X11/xserver/SecurityPolicy
Could not init font path element /usr/X11R6/lib/X11/fonts/CID/, removing from list!
/Applications/MacRadiant.app/Contents/Resources/sw/radiant14/games/trem.game:1: parser error : Start tag expected, '<' not found
{\rtf1\mac\ansicpg10000\cocoartf824\cocoasubrtf420
^
xterm: fatal IO error 32 (Broken pipe) or KillClient on X server ":0.0"
Quitting XDarwin...
hope this helps