Mjauv: I am by no means a fan of the practice but the DLC is meant to bait people into using Galaxy, not to prevent piracy. Calm down a bit bro.
Actually, everything that binds users to a client software is a form of DRM.
This is quite openly stated in Steam's DRM description:
"The Steam DRM wrapper is an important part of Steam platform because it verifies game ownership and ensures that Steamworks features work properly by launching Steam before launching the game.
The Steam DRM wrapper by itself is not is not a anti-piracy solution. The Steam DRM wrapper protects against extremely casual piracy (i.e. copying all game files to another computer) and has some obfuscation, but it is easily removed by a motivated attacker.
We suggest enhancing the value of legitimate copies of your game by using Steamworks features which won't work on non-legitimate copies (e.g. online multiplayer, achievements, leaderboards, trading cards, etc.)."
(emphasis added)
GOG Galaxy is simply following the same route while publicly stating that it's not DRM.
Steam is honest about it, GOG is not. Ironic, isn't it?
Now how much difference does some cosmetic DLC make?
Personally I wouldn't be bothered to care, but as a practise, it's not something that I would appreciate at all.