this is the officially released GPL source code by Asus, used for compiling firmware version 1.7.5.6

you can find it here for downloading:
ftp://ftp.asus.com.tw/pub/ASUS/wirel...3/GPL_1756.zip
ftp://www.asus.it/pub/ASUS/wireless/...3/GPL_1756.zip
http://www.asuscom.de/pub/ASUS/wirel...3/GPL_1756.zip
http://www.asus.com/pub/ASUS/wireles...3/GPL_1756.zip
http://www.asus.com.cn/pub/ASUS/wire...3/GPL_1756.zip

mirrored @ chupa.nl: (please only use this link when the others are dead or veryvery slow)
http://files.wl500g.info/asus/wl500g/gpl/GPL_1756.zip