It comes at an interesting time, since there was a bit of an issue with the HITMAN release that ended up being pulled down since it required online to do a lot and unlock a lot of things. GOG is well-known as the DRM-free store, and this isn't exactly changing but they're tweaking what they mean by it.
They talk a little about how things have changed, and that some "of the most infamous DRMs of the past are thankfully long gone, it doesn’t mean the constraints are fully gone". It is a complex thing, as they say, as so many games now offer online features even for single-player titles, so GOG has more of a plan to handle them now.
Here's the three main points they will stick to:
1. The single-player mode has to be accessible offline.
2. Games you bought and downloaded can never be taken from you or altered against your will.
3. The GOG GALAXY client is and will remain optional for accessing single-player offline mode.
Point number 3 is an interesting one, as it's only optional for single-player. There are already a few games that use the Galaxy API for multiplayer instead of a standalone solution.
They also said they will continue to "make games compatible with future OSs and available for you for years to come".
When it comes to multiplayer "games with those features belong on GOG", although they will be updating the GOG store to let you more easily discover them and add more info to store pages to help better inform potential buyers.