zmagnum: The steam copies are steamworks drm only, yes?
As far as I know. It would be rather odd to put additional DRM on a steam version when you're giving DRM-free copies to the very same customers at the same time.
In fact, some Humble games are DRMless even on Steam. Take Super Meat Boy. Install the Steam version and try to run it without the Steam client. It works, without launching the client. And it still keeps track of your progress and achievements, which it sends to Steam the next time you start the game when the client
is running.