GOG Galaxy is an online client, it is that which is requesting net access, not the game. It is not DRM. If you don't want your firewall to bug you, don't use Galaxy, run the game manually -- it (the game) does not require internet access.

but closing galaxy and starting via the .exe in the directory produces the same results.

hm i don't know if it is some strange firewall problem (i don't have a software firewall) but i just tried Witcher 3 with internet but Galaxy off and without internet and Galaxy off.

Result: Starts without any problem.

yeah, tried again with deactivated Lan/Internet but with access to the (disconnected)internet and witcher starts.

well, i have to say it doesn't need an active internet connection but for me, it at least must not be denied access even if there is no connection.

It sounds like you have your firewall misconfigured. The game, without Galaxy, does not require internet access, period.

Application firewalls also might block you from executing program altogether depending on your settings. Might wanna check that or simply reset firewall settings to default.

My firewall says that Witcher 3 is trying to acces IP address 127.0.0.1 - this is "localhost", basically connecting to the same computer you're running the game, not an outgoing connection. Not sure why it needs that, I guess it's for communication with Galaxy (maybe achievements, for example).

You are right there is Digital Restriction Management at work, others tend to not acknowledge it and I gave up on getting into a discussion about it.

You asked why they need an active Internetconnection, here comes the answer:
They are monitoring or are able to monitor everything you do in the game in realtime, they do contact a server on a port which according to RFC 1700 runs syslog: http://linux.die.net/man/8/rsyslogd

You might now think how can I escpae that:
Rename .\The Witcher 3 Wild Hunt\bin\x64\Galaxy.dll to Galaxy.dll.orig
Rename .\The Witcher 3 Wild Hunt\bin\x64\goggame-1207664643.dll to goggame-1207664643.dll.orig
Block the game in your firewall
PROFIT

For those who wonder what I mean by Digital Restriction Management, have a read:
http://drm.info/what-is-drm.html

That is Galaxy, an online client, not the game. Duh!

@passionata
try to be better next time troll...

"Digital Restrictions Management (DRM) is any technology that is built into an electronic product or service with the aim of limiting its range of uses after purchase."

Yeah i am so limited by Galaxy or the Game itself i can't even think of one point... from which crazy planet are you? Go whine about the crap Microsoft is pulling with Windows 10 or Steam im general...

It wants an internet connection, but it doesn't call outside the PC. It isn't DSRM because even without my internet active, it still works perfectly well. Being monitored is not DRM. It has it's own concerns, but don't equate the two.

So I was playing around with some issues with GOG Galaxy (DLC wouldn't DL), and I uninstalled the client. I then found I could still launch W3 and play it without Galaxy installed. Not sure if it is a bug, but seems to solve your "DRM" issue.

It's not a bug at all. Witcher 3, like all games on GOG, is DRM-free. The Galaxy client is completely optional, and you do not need it to install and play GOG games, even if they were installed through Galaxy.

Hmm it doesn't try to access the itnernet for me. In fact it doesn't even have an entry on windows firewall...