A demo would be very nice. This game is currently flying way below the radar; I've known about it almost since it debuted, but only because I routinely scour aggregators, feeds, and blogs pertaining to indie, base building, and space-related games. Back in 2011-2012, there hadn't yet been a massive explosion of indie titles, so it was a lot easier to find. I show Starsector to friends who I think might enjoy it, and the videos and sprites always impress, but they can't get it on Steam et al. yet, so there's a general reluctance to buy it right now.
The "soft DRM" currently consists of an emailed download link and (what I assume is a hash) activation code, so I imagine distributing a demo more freely might create piracy concerns. Alex seems very active on the forums, so no doubt he'll pop in here with his actual opinion, which will be more informative than my idle speculation.