I found a way to connect a serial device (my domotics system) to the WL500g deluxe and remotly control the domotics system over the ethernet.
I downloaded the ser2net program from sourceforge.net and cross compiled it for the Oleg firmware. Thanks to the very good tutorial from macsat. The ser2net program makes it possible to connect a serial device to the ethernet. It is all configurable by a .conf file. The serial device is connected to an USB to RS232 converter. I found here on this forum a driver for my converter that works with the Asus. The PL2303 driver.
You can install the necessary drivers with the following commands :
insmod usbserial.o
insmod pl2303.o
mknod /dev/ttyUSB0 c 188 0
chmod 666 /dev/ttyUSB0
In the ser2net config file you have to change the tty device to /dev/ttyUSB0
I attached the neccessary files for who is interested in it.