Actually yes it is... I have it installed in Galaxy alpha. :P

Then so is the autoupdater, because updating is all it does.

You do NOT need to log in or even load the updater to play the game. Whoever made that claim earlier was mistaken.

Really ? I have it installed (in the same folder than the other Galaxy games) and it wasn't detected... will need to retry...

You probably need to click install again via your library, just be sure you have Galaxy pointing to the right place for the GOG games and it should pick it up and download only what is needed.
There biggest issue here for them is that there is no easy way to back up updates after you get them for a re-install if needed, so they feel it is DRM (even if it really isn't) that, and that the standalone installers aren't updated as quickly. Fair complaint, but a absurd one when Galaxy isn't even done yet and all of it's features isn't even there. People see Galaxy and think Steam, but Galaxy is far more forgiving and flexible even in it's early state. People need patience, GOG knows & understands why we buy games from them.
Also Galaxy won't pick up any game automatically if the game was installed with an old installer, even if the game is supported. You have to manually re-install it from you library so Galaxy can add what files that are needed.

It's not.

I can perfectly understand the fears of the people in this thread.

Steam was introduced the same way to the owners of Half-Life and Counter-Strike. Valve dropped standalone patches, did shut down the WON servers (non-account based DRM scheme just checking CD keys) required for Internet multi-player, and forced people tying their retail game to a Steam account - thus making all retail games (and their CD keys) worthless this way.

To make it even worse, this plan was not communicated before the sale of the game, not even to the initial publisher (Sierra). It was retro-actively introduced DRM - the worst kind of it (could only be surpassed by suddenly asking for subscription fees, but that is technically still possible with Steam).

1999? And I think that it was about then gOg started to work on Galaxy also....