DD-WRT is free Linux-based firmware for several wireless routers
HairyDairyMaid_WRT54G_Debrick_Utility_v45.zip
http://www.dd-wrt.com/site/support/other-downloads?path=others%2Fwrt54gv5+flashing%2F
wrt54gv5 flashing
http://www.dd-wrt.com/site/support/other-downloads?path=others%2Fwrt54gv5+flashing%2F