>>139
Even indie games have Steam achievements, so it'd require making a separate build of the game, at the very least. Cloud saves also, maybe. The Steam "emulator" linked earlier also suggests devs use it to simplify republishing games:

If you are a game developper and made the mistake of depending too much on the steam api and want to release of version of your game without it and don't want to rewrite your game, this is for you. It is licenced LGPLv3+ so the only source code you need to publish is the source code of this emulator (and only if you make modification to it).