Broadcom has released its Linux 802.11n drivers as open source code: Drivers for several current chips are part of the full-source code release. This may seem obscure for wide consumption: why should you care what the relatively small market of people using Linux on a laptop do?
It's actually a big market. Versions of Linux are used on hundreds of millions of digital appliances, in which an "embedded" form of the operating system is used (one designed to be limited and robust to carry out a specific set of tasks, like driving digital video recorder).
Atheros went open source on a set of its drivers in 2008; Broadcom, for competitive reasons, may have needed to join them in 2010.