Fresh Tomato
FreshTomato is a firmware project based on Linux, targeting home and SOHO routers. FreshTomato is distributed on the GPL license GPL license.
FreshTomato supports Broadcom based systems. Features a particularly friendly interface, which can be used by even inexperienced users.
I currently run Fresh Tomato firmware on two R8000 Netgear Nighthawks. It is far superior in both security and features than the original Netgear firmware that came with these routers.