Will Atheros 9285 Ar5b95 Ar9285 work with free software?

I'd say yes, according to this. Supported by ath9k kernel driver, no firmware needs be loaded from user space.

https://wiki.debian.org/ath9k

Atheros AR5BXB92 is a full-length mini-PCIe card that uses AR9280 chipset, is 2x2:2 MIMO and has dual-band support for A/B/G/N. Can usually be found for around $15 USD. IMO worth the upgrade over the ar5b95 single band, single stream $5 cards.

Atheros AR5BHB92 is the half-length variant of the same.

I have both and they work fine in my Libreboot laptops (X200 and T400).

OK, but any improvement is here over b/g in real life?

It will work fine but don't buy from Amazon :)

https://www.amazon.com/Qualcomm-Wireless-AR5BHB92-Dual-band-Compatible/dp/B00JESLUWQ/ref=sr_1_1?s=pc&ie=UTF8&qid=1468271512&sr=1-1&keywords=dual+band+atheros+half+mini+pcie

Will this card work without proprietary software? Also will it work for dell inspiron n5050? inspiron n5050 has a half mini pcie slot.

what is dual band? does that mean it can utilize 2gz and 5gz?