Complex sentence: DD-WRT is a Linux-based firmware for several wireless routers, most notably the Linksys WRT54G (including the WRT54GL and WRT54GS).
Split into simpler sentences: DD-WRT is a Linux-based firmware for wireless routers. It works for several routers, most notably the Linksys WRT54G series (including the WRT54GL and WRT54GS).