I read that all players can interact in the same universe in this game. Does that mean it will require an Internet connection, or not?

Whoops, sorry. I found the answer posted elsewhere. Supposedly it will not require the Internet.

Where did you find the answer?

Kind of an aside to that question how will the universe actually work? If I buy on GOG will I be in the same universe with the possibility of running across, or possibly hooking up with, my friends who buy the game on Steam? Or will GOG's version be on it's own servers/multiplayer system like a lot of the other games that don't cross integrate well due their heavy use of Steam's system when purchased over there?

Well, according to the game's both gog and steam pages it doesn't even have any multiplayer.

Heh. I don't think many current developers even understand the meaning of singleplayer.

If it doesn't have offline singleplayer it's not my cup of tea.

I think I can answer all these questions now. The way I understand it, there is a single-player offline mode (I found that answer in the comments section for the game on this website). If you play it online, I'm not even sure that players can see each other or interact. I don't know. The universe is HUGE compared to the number of players (or even the number of people who've ever lived on Earth), so I wouldn't expect them to meet very often anyway.

I did read on Wikipedia that it resets the position of items on each planet when you leave, so it won't have to save all that information (though things can evolve over time), which implies that each person has a separate experience, but they can all visit the same planets, because it uses the same seed for all random number generation so it happens the same for everyone.

The main reason for having it online at all is because whenever anyone finds anything new, the person who discovers it can name it and catalog it into a built-in encyclopedia stored on the main server, and everyone can access that information and possibly add to it. People are given a bonus for discoveries.

While you play it offline, you don't have access to any of that, but I think you can connect it online later and then use it or add to it.

Before i purchase the game here....

I read(for example here: http://www.gamespot.com/articles/no-mans-sky-will-have-traditional-multiplayer-but-/1100-6420982/ ) the NMS will have a Multiplayer System of some sort.

Is it possible to access this mode with the GoG-Version, or is it just offline singleplayer?

If the gog-version also features this online mode will this be compatible with the steam version of the game?

I think it's too early to be asking these kinds of questions, the game doesn't come out until June, I think? All the answers people will be getting are speculation by other people who've read gaming news sites' previews.

The only ones who could definitely answer these types of questions would be the devs or at least a "blue" GOG staff member, but those have been kind of absent from the forums, lately.

I don't want to speculate, so I'll just say that, at this stage, I honestly don't know. All I know is that I trust the devs, I know they're pouring their all into this game, and I really think it's going to be amazing when it comes out.

I don't want to speculate either, thats i was asking and i hope that someone like JudasIscariot will shed some light into this.
Because this is a Preorder i want to have those questions answered before i buy, or the Preorder phase is over.

I would like to buy the game here on gog, but if the gog version is SP only i will rather choose the steam version and later, when the game is on sale i will buy it here again(just for archive and drm-free reasons).

I had the assumption the multiplayer feature or whatever it is will be more like this game:

http://store.steampowered.com/app/252290/

Well, GOG sels DRM-free games that can be played anyway and anywhere, that will be strange if NMS will be online only or MMO (DRM some sort) game. So basicaly it will have offline other way it can't be sold here.

It can be played completly singleplayer and offline. But can the gog version also be played online features(the atlas and so on))

Probably via GOG Galaxy. Kind of makes sense as its the only thing GOG has that's Steam like.

We only know what has been said, multiplayer will mostly be something where you record and upload your journey for others to see. You will utilize some alien technology in game called Atalas, which acts like some kind of online repository for collecting your exploits. Devs have also said since the sheer number of stars/systems being used in game makes it highly impossible for two players to even meet up in game. Some corny theorists believe end game content will be a giant party bash and you get to meet everyone, their take on reaching the center of the galaxy.