Is Dustforce DX a separate game to Dustforce?

I have the exact question

As of now, you can enable DX as a beta. The code is "dustforcebeta".

Judging from this it appears to be an update for Dustforce.

Its a beta. You already have it if you have Dustforce.

http://www.reddit.com/r/dustforce/comments/2izxmg/dustforce_dx_beta_live/

According to Humble's own site:

Dustforce DX is an update to Dustforce featuring over a dozen new maps, new and improved overworld, bug fixes, new music track and some of the best community made custom maps pre-installed.

Note: The DRM-Free version for Windows is the DX version of the game, Mac and Linux DRM-Free versions are the core version and will be updated on the download page once they are released.

As others have already mentioned, it's just an update. Additionally, if you try to activate it on an account that's already got Dustforce in its game library, you'll just get an error saying that the game is already owned.