One of the actual problems in developing a free operanting system are the wireless devices. Some manufacturers forces to make inverse engineering to avoid the lack of specifications.

Some forces to use a closed firmware. Even some plugs a HAL (Hardware Abstraction Layer) that taints the kernel. Some weeks ago The Jem Report published an interesting article about this question, an they included the interviews that friendly manufacturers: Ralink, Atmel, Realtek answered (unfriendly ones: Atheros, Intel, Broadcom, Marvell, Texas Instruments refused to talk).