Oh, I thought the Humbles usually included DRM free versions, too. Or maybe that changed in recent years.
It seems that the Humble Indie Bundle no longer requires that devs/publishers offer a DRM-Free copy of their game in order to take part in the bundle. About half of the bundle (Including all of the highest tier) didn't have DRM-Free copies.
Beat Cop did include the DRM-Free copy though. And it was in the lowest tier. So in theory, if one only wanted the DRM-Free version, they could have had it for as little as a penny.