This is a technical issue that needs to be addressed by the enhanced edition devs. I suggest asking in the forums where the devs hang out.

Non-developers can help with this issue. And I have worked around the issue. I added
[code]
composeAll
[ className =? "BaldursGate" --> doFloat
, className =? "BaldursGateII" --> doFloat
]
[/code]
to myManageHook in xmonad.hs and wrapped the launcher script with another script:
[code]
#!/bin/bash

title="Baldur's Gate - Enhanced Edition"
exec gog-baldurs-gate-enhanced-edition &

geo=$(xrandr | grep primary | cut -d ' ' -f 4 | sed -e s/-/+-/g -e s/x/+/ | sed -e s/++-/+-/g | sed -e s/+/,/g)
geo=0,$(echo "${geo}" | cut -d , -f 3,4),$(echo "${geo}" | cut -d , -f 1,2)

c=0
while ! lsw -l | grep "${title}" >/dev/null; do
sleep 0.2
: $(( c++ ))
if [ $c == 10 ]; then # 2 seconds
exit 0 # sic
fi
done
exec wmctrl -i -r "$(lsw -l | grep "${title}" | tail -n 1 | cut -d ' ' -f 1)" -e ${geo}
[/code]
(And similarly for BG2:EE.)

The only issue now is that the window lets the mouse leave the window, but
of course that is easily worked around by disabling all monitors except the
primary monitor.