With regards to Aspyr being dumb, yes, I fully expect them to be as dumb about DRM-free games as much as any other publisher. Perhaps even more so, due to cost of Mac-native ports still being relatively expensive to produce and support, and given their lower general potential for profit.
With regards to Apple, I highly, highly doubt that they're causing the hold up with Aspyr's Mac-native ports coming to GOG. I don't see any clear benefit for them (I highly doubt that games like KOTOR/KOTOR II being available on GOG are going to seriously affect the popularity of games on the App Store). Just because Apple is mentioned as a distributor doesn't
necessarily mean that they have control over where the game can be sold. Does
Steam have that same power over publishers and developers?
The only way I could see that actually happening is there was some kind of Bayonetta 2-type situation, where Apple signed some kind of exclusivity agreement with Aspyr in exchange for Aspyr getting funding for their Mac games. It's not impossible, and it's not without precedent, but without any hard evidence it's difficult to say. As noted earlier, historically, the only recent times Apple have ever gotten directly into gaming on OS X was when they needed titles to show off at public events. (It is possible that Apple may have paid EA to do their in-house ports of BF2142 and C&C3 way back when, though.)
My own personal guess -- and it is just a guess -- is that we haven't seen Aspyr or Feral's ports due to the reasons why we haven't seen other major publishers on GOG; a combination of apathy towards DRM-free games, fear of piracy, and a general level of comfort with Steam. Add to that that the ST/SW games are licensed properties, and that adds another layer of complexity. Sure, GOG has an agreement with Disney/LA, but there's probably another level of negotiations that need to be worked out with Disney/LA and Aspyr or Feral, too.