If Steam is selling the games as "DRM-Free", connecting to the client is probably more to do with collecting statistics about how you are playing the game than preventing the game from playing. GOG is doing the same thing with at least some of their games. No matter whether you have the GOG Galaxy client installed or not, the game exe has been altered so it will reach out and try to connect with Galaxy -- and Galaxy, if present, will send information out on the Internet. In other words, GOG and Steam are attempting to "monitor" your playing through their clients, but not actively trying to prevent the game from playing.
For example, Dreamfall Chapters (and most Telltale games) have a "feature" where the game compares the "decisions" you made with the "decisions" other players made and displays this information when you reach the end of a chapter/episode. It also collects and sends out information about any so-called "Achievements" you got (should the game be infected with those). Both the Steam client and GOG's client will do this, even though GOG claims to be "DRM-free."
If you don't want the GOG client to send information online, you can disconnect from the Internet before starting and playing the game. However using a software firewall to try to block the game from connecting with Galaxy will result in the game not starting, no matter whether you have Galaxy installed or not. Oldmariner discovered this with some of the GOG games he reviewed. This "feature" has also been added to GOG games like Noctropolis (a DOS game from 1994). If you want to know if a GOG game has had this "reaching out" inserted into it, I suppose you can check whether the exe is from before GOG introduced Galaxy or not.
According to
***Wikipedia***,
In the CD Projekt RED company update in June 2014, GOG.com announced that it would be bringing a Steam-like client, GOG Galaxy, to Windows, Mac, and Linux platforms.
So any game exe's from GOG from before June 2014 probably don't have this "Galaxy integration," but any "updated" exe's from after that
may have had Galaxy integration added.
According to GOG support, the game won't send information out on the Internet if Galaxy is not installed. But the fact that blocking its probes with a software firewall prevents the game from starting is troublesome for people who care enough about what information their computer is sending out on the Internet to have a software firewall configured.
Anyway, this issue of "DRM-free" Steam games connecting to the Steam client is probably the same as what GOG is doing with Galaxy. If it bothers you that a single-player game is sending information about how you're playing out on the Internet, then the GOG client should bother you as much as the Steam client.
Is it bad?
That depends on how you feel about information being sent out online. The information seen by other players may not be personally identifiable -- information displayed at the end of chapters is an aggregate. But the server may also record other information like who you are, the specs of the computer you're using to play, what part of the world you're in, what other games you've played, etc. You have to decide for yourself if you think that is an invasion of privacy, something you don't care one way or the other about, or something potentially useful to you (if you like to compare when or how fast you played a game and what decisions you made with the stats of other players).
DRM means "Digital Rights Management." Do you consider "Digital Monitoring" to be a type of Management? Or is the lack of a disc-check or lack of online activation sufficient to qualify as "DRM-free." Or do you consider it unwanted spyware?
With Steam, at least you always knew you were going to have their client. With GOG, you purchased games under the impression that any alteration to the games was to make them run better -- not to spy on you. How many people bought GOG games because they wanted to be tracked and have information sent out online? IMO what GOG did is a bait and switch. IMO it's the equivalent of buying a book, and having the person who sold you the book follow you around, noting down when and where you read the book, how long it took you to read each chapter, whether you showed any part of the book to another person, comparing how fast you read the book to how fast other people read it, etc., and then trying to sell you on the idea that this is an advantage to you because now they can tell you how long it took you to read the book and how much faster or slower you were than other people. IMO this is not an advantage. It is creepy and equivalent to stalking. YMMV
My issues with Steam are more about other things, like their spotty customer support (success in getting help from them is all over the map, with some people getting help very quickly and others unable to access their accounts and waiting months for resolution). GOG and Big Fish are more reliable for customer support.