I am sorry, I should have taken the time to be more specific / used quotes...

It was just my intention to answer your second question - not the first one.

It does mean that there are drivers for the HD5000 series. The new kext files do even mention your cards device ID.
But there has been no one who has figured out a way for a working inject, yet.
Means the drivers are there, but currently there is no method to use them for your card. (More difficult job than it might sound to be.)
So if I were you I wouldn't give up hoping for a solution coming up in the close future and stay tuned.

---