Since Abyss Odyssey is mentioned in this thread I'm just going to post the link here. Yesterday I asked the devs about a GOG release, here's their response:
Hello ACE Team,
Do you have any plans to bring this game on GOG.com? And if not, can you please give a reason why.
The game looks great and being a roguelike it certainly packs some great replay value. I like rougelikes and this would certainly make a nice addition to my collection, however I don't like Steam and DRM in general. Bringing the game to GOG would certainly net you more fans / customers and increased profit.
Thank you for reading.
Dev response:
Unfortunately no. The game works with Steamworks, so there is no way to separate it from Steam.
Link to thread:
http://forums.aceteam.cl/index.php?showtopic=4294 Shame, this game looks promising.