If they'll let us use serial keys we'd be happy to, I imagine. And I dunno if GoG itself is really all that draconian about it (even if some part of its forum population is).
For us the serial keys are basically zero protection from piracy (they don't check in with our servers, so everyone in the world could be using the same AIW key and we'd never know the difference). Piracy-prevention isn't the point for us and we don't think it's possible for our kind of product anyhow.
The point is that it lets us have exactly one version of the game to support that is both the demo and the full game: the only difference is whether you've entered the serial key. That avoids the need to redownload after you buy, and keeps the demo fully up to date automatically. So basically we reserve the right to do good customer service, even if it involves something that triggers DRM-allergies in the idealogical
I imagine the main reason we haven't pursued getting on GoG has been that we don't expect a significant revenue increase adding that one extra distributor, and we do expect at least a little (good-natured) wrangling over the serial keys thing, so why bother?