It really doesn't matter, the actual RF baseband inside the chip is still closed source. Atheros never released it for any model. The firmware interface to the OS driver, yes, but not what's going on under the hood.
But they have to go with some weird, ancient 802.11n card instead of a modern 802.11ac 3x3 MIMO, dual band Intel chipset card, because they don't like the binary blob in the ROM of the Intel minipci-express card?
At some point in time you have to trust the devices you're attaching to the pci-express bus in an x86-64 system or you won't have any useful functionality left.
Anyway, the more open components the system the better, and if this shows there is an interest for an more open system, the next one might be more open than this.
Not so much for the firmware blobs the vendor maintains in the "linux-firmware" kernel.org repository and that are absolutely required for the device to function.