I believe there are only a few Bluetooth chipsets from Atheros available and
these include the: AR3001, AR3002, AR3011, and AR3012. All of these use the
ath3k driver/firmware. The driver is free software friendly although the
firmware is not.
I would suggest avoiding boards with Atheros bluetooth for the moment.
Although this is less of a concern than getting a board with say an
NVIDIA/ATI graphics chipset. Atheros has been very cooperative in releasing
code whereas NVIDIA/AMD have not (at least not sufficient code/specs). The
majority of companies do not release source code for firmware.
Until we can get Atheros to release the source code to this firmware I'd
suggest getting a USB dongle with a CSR chipset. This is fully supported in
GNU/Linux.
https://www.thinkpenguin.com/gnu-linux/penguin-usb-bluetooth-micro-adapter
