The new game Master of Orion requires us to have running GOG Galaxy in order to access and play the Multiplayer... Isn't the whole point of GOG is to free the users from having / requiring us to having a third party app running along side of the software for it to function fully?

It's not a good sign for GOG, soon i can see that GOG will just become another Steam clone if they are not careful..

The other option, which GOG has certainly used earlier (e.g. the Full Spectrum Warrior games, Brutal Legend etc.) would be that the GOG version has no multiplayer at all, ie. cut content. Would that have been preferable to you?

you mean galaxy isnt already that ?

and its been well known for a while now that multiplayer needs to be routed through gog galaxy

Gog have said multiple times since their creation that they could only guarantee the DRM-free part for the "single player" part of games, not for the multiplayer.

We already had in the past games that required, for multiplayer, online activation, registration and login on the developer online service, etc...

Galaxy is just a new "alternative" for games that would otherwise have their multiplayer disabled.

Have they?
I don't think I've ever read an official statement that said that.

GOG stated multiple times some games will require Galaxy for Multiplayer. As long as it's only for multiplayer I'm fine with it, although doesn't exclude the fact that I'd prefer an LAN ir Direct IP option but that's a Dev choice not GOG's.

Yes they have mentioned it multiple times, either on the site or on blue remarks. As you can imagine it's not a new topic at all and was brought countless time, especially every time that a game requiring online activation / registration was being sold. (e.g. Two World, AoW III, etc... )

From GOG's own store-page for the game (emphasis and underlining is my own):

'Multiplayer Notice: GOG Galaxy is required to play multiplayer. '

To me, GOG Galaxy seems like GameSpy. You didn't need it to play single player, but it was mandatory for multiplayer in many games back in the days. AFAIK, the only multiplayer mode which doesn't require any client is LAN.

Yeah, that's kinda my take on it as well. I don't do MP, but love being able to play many game's SP campaigns, without having to install/use some kind of client that I intend to never use like Galaxy, Steam, ect. It's nice to have a choice...and to those who like MP, have fun bruh