Spinorial: Not supporting the DRM-free version, I can understand. It's bad, possibly deceptive, but understandable. But removing the last DRM-free version from your library seems like a step beyond that. It's a very bad precedent, and Humble should not be able to do that without prior notification.
If this trend continues it will likely have a chilling effect for developers as well. I know I will be less likely to support any in-development game if the prevailing attitude becomes "DRM-free is fine at the beginning, but once we're a success you can go screw yourself".