Redux FAQ: https://steamcommunity.com/app/401680/discussions/0/3572873
original post: https://web.archive.org/web/20160810033958/http://steamcommunity.com/app/401680/discussions/0/357287304428353574/
Q: Will there be a DRM-free release on, say, GOG.com, or perhaps a boxed edition?
A: All of our games on Steam are DRM-free, and Redux is no exception. Though the game uses Steam for distribution and installation, it doesn’t actually use the Steamworks DRM, so you don’t need Steam to run it. After Redux is installed, you can freely uninstall Steam and continue playing, if you so choose. We will be putting Redux on GOG.com in the future, though.
GOG has been removed from the FAQ and the game likely won't be released there.