If you purchase a game it remains in your library even if the devs/publisher decide to pull the game from gog.

Sure it can.

At least one example of something like that happening has already occurred, wherein GOG permanently deleted a game manual of out everyone's library who had purchased the game (I think the game was Jagged Alliance 2 IIRC, but maybe I am misremembering), on the basis that GOG had made that game manual available even though (unknowingly to GOG at the time) they didn't actually have the legal rights to do so.

No reason exists as to why the same thing couldn't happen with a game itself too. It could.

Maybe some could argue that such a thing is unlikely to happen, but certainly it's possible.

The Crew was removed due to being a defunct, DRM-saturated, online-only game that was rendered worthless once the servers closed. There's no similar incentive to do that for single player games on GOG. In a more practical sense, the whole point of downloading and backing up GOG's offline installers is that you'd still keep your game even if that did happen / the store closed.

Technically, every game store must have a way of deleting a title from an account due to fraud (eg, game purchases bought with stolen credit cards need to be revoked). I'm pretty sure it's part of the contract between GOG and publisher that if they remove a game from GOG, it must remain in buyer's accounts (as a legal requirement). Hence why the various games that have been removed from sale on GOG (eg, Duke Nukem 3D, Gray Matter, etc) remain in our accounts. Ubisoft probably got away with it due being a 1st party title (Ubisoft game sold on Ubisoft's own game store) and knowing full well it was a "Game As A Service", they probably had no similar publishing agreement clause (or ever saw the point of one).

Yes, technically and legaly the people who holds the license can remove it completely from your account.

It has never happened yet, neither here on gOg or any other DD store I know about (e.g. Steam, Origin or Epic). I also do not think it is very likely to happen, if it does it would be due to some major legal problems (for example if a game is shown to be a complete and direct plagerism and the original right holders demands the game to be removed). But if we are talking hypoteticals, then they can do so.

That is not correct, it depends on the license and the legal agreement between licence holder and GOG.

If the licence holder agrees in the legal agreement that those who purchased a game on GOG will have granted access after the licence expires, then it would not be legal to remove the game from the accounts. And GOG could refuse to do it. And I belive that this kind of provision may be included, as GOG advertises their games as "keep your games forever", so if they would have to remove such game, they would have to give the money back to their purcharsers. .

There's also a few details:
- goodies (like manuals) are not games, so they may be removed
- what I wrote above doesn't apply when GOG doesn't have legal agreement with all the licence holders, in most cases when it will be discovered after the purchase that copyrights belonged to someone else (partially or as a whole). In such case they could be forced to remove games even from the accounts (but they would gave money back to their customers). I belive that this happened with Death Gate game - it was released by Ziggurat and then probably authors of the IP asked to withdraw it from the sale (I suppose the licence to use their IP expired). But even in this case, I think that GOG did not remove the game from the accounts.

It's a website, so of course it could. But, you get offline installers that you can store on your computer or upload into cloud storage if you are worried about that. It's what I do.

The issue with Death Gate was that it was (re-)released prematurely without clearance from the authors of the books it's based on? If I remember correctly...

And yes, I still have my copy sitting in the library as it was just delisted, and not removed/taken from people who managed to pick it up before the cease and desist.

No, it is inherent in all license agreements that a license can be revoked, as the owner is the license holder. You may find licenses where the license holder agree to never revoke the licnese, but this is far from being default and will be very rare

In essence:

Make sure to ALWAYS download the offline installers (as well as the digital extras such as soundtracks, artbooks, manuals, etc) of the games you purchase and you're good.

This is again not true. In a pre-digital world it was called The principle of exhaution. You could not revoke a licence for a computer game (sold on CD) after its first sale by the copyright owner or with their consent. Even if you were a licence holder.

And it should be also applied to the digital sales of immaterial games. It doesn't matter what is in the licence agreement included in the game, it cannot be revoked.

And while GOG legal agreement (licence to sell games) may be revoked any time, the licence holder cannot revoke a licence to your game, because of principle of exhaution.

Not to mention a whole lot of consumer laws that would also matter if anyone would try to revoke such licence.

I see, first of all thanks a lot for all the insight that you guys are contributing!

For my understanding, this subject seems to not be written in stone here on GOG. Even tho the company vision is "keep your games forever" - which I very much agree and is the main reason I am now using GOG as my main PC platform - by the discussion so far it seems to be a matter for legal debate.

Still, the offline installers will be the way to go on my part (Althogh I am still deciding which media to use as storage). The main reason of the question is that some of my games are new and may have updates in the future or eventually some new version of Windows might come out and there may have a update as well, so the download-when-necessary aproach would be very handy.

As others have said, download and backup your offline installers and they'd have to break down your down and physically prise the backup drive out of your hands to take it away. ;-) For newer games suffering from "update spam", yes it can be awkward to keep on top of them if you try and back everything up on day 1 (though I just wait a while to buy them in the first place given the rough state they are released in). For older ones that are long finished though, this place is as good as permanent ownership will ever get. Certainly compared to Ubisoft's $60 Rent-ware.

The principle of exhaution, also called The First Sale Doctrine, applies to physical goods containing IP materail, and basically is used for being able to re-sell those goods. What it means is that if I invent a new type of mouse, i can get a patent on that mouse design, and thereby limit who can make it and initally sell it. However, if you as a customer buy my new mouse, I cannot stop you from selling that mouse again if you want to re-sell it.

An extension of this is the axiom that basically says "the license follows the medium". You are right in the wording "it should" apply to digital sales, bacuse it does not. Since there is no medium to follow, it also means that The principle of exhaution does not apply.

it is very easy to figure out if The principle of exhaution applies to digital goods - sell me one of your gOg games. if you can, then it applies - if you cannot, then is does not