Atheros has released an open-source version of the driver software that talks directly to its chips: The company has long maintained that it required a closed HAL (hardware abstraction layer) to prevent rogue developers from changing settings in its Wi-Fi chips that would cause the chips to perform activities that were against its interest. For instance, it's a/b/g chips can use the 4.9 GHz band, which is illegal in the U.S. and many other countries, but allowed in Japan.
Those objections must have been overcome, as the firm is providing a full, ISC-licensed free software code base for their HAL for 802.11a/b/g chipsets. This should allow the ath5k project to create a fully Linux kernel integrated driver for Atheros chips with no reverse engineering or licensing issues.
This opening up of the HAL allows laptops and handhelds running versions of Linux to have more effective use of the Wi-Fi adapters built in or that can be added on. Note that Atheros hasn't opened up its 802.11n chips yet.
This HAL isn't the same as the one used by the Madwifi project, headed for several years by Sam Leffler. Leffler was able to start Madwifi up by signing an agreement with Atheros that let him write a binary HAL that could be released alongside open-source or free drivers. Leffler reiterated a few days ago on a mailing list that his HAL still wasn't available for release. And, at this point, the Madwifi project appears to be deferring to the ath5k folks. (Confusingly, information about ath5k is all noted at and accessed via links on the Madwifi site, but it's a separate project.) [news via Thomas Gee, Canard WiFi]