I've seen reports that suggest that AMD may be changing gears and giving a
bit more support for Open Source drivers, although I may be missing
something, since it's not clear to me if we'll be seeing anything like 3D
acceleration as part of this change (I'm relatively clueless about this
stuff).
http://www.phoronix.com/scan.php?page=news_item&px=AMD-Two-More-Open-Linux-Devs
I found a 2014 talk by and AMD engineer working on open source drivers:
https://www.youtube.com/watch?v=hOmNWxx4Cwo
But with recent reports of Nvidia trying to block the Nouveau project on
their new cards, it seems AMD and Nvidia cards might be swapping places
overtime, with Intel hanging out doing what they've done.