In TWAU Humble store page the game appears as an only steam key purchase. Actually when bought you can see there's the option to use a TellTale key to activate on the developers site ( http://www.telltalegames.com/redeem ) I'm not sure if it's an one-time activation(most likely) or there's a limited simultaneous installations trough pc's (apparently no) or else. I'm not sure if this could qualify DRM-FREE but you can download both on HB and on TT site.
here:http://i.imgur.com/AvdyJsV.png.
I hope this could help. I didn't find anything about.