Yes, Gale will be on Defiance, eventually, but no one has stated what episode that will be. There's one main character that is all white (Datak)... in one scene, for 2 seconds, he sounds exactly like Gale, but other than that he looks and sounds nothing like Gale. Even with all the make-up I think we'll know Gale when we see him.
There have been 4 episodes so far, and he hasn't been in any of them. However, like most TV shows, read all the opening credits, Gale's name will appear in the episode he is in... when that eventually happens.
According to Gale his character will be a story arc; @DefianceWorld said that Gale will be playing an old flame of Amanda's (mayor)... so I'm assuming he'll be human, but you never know with this show.