skeletonbow: I did too and waited forever, but after seeing it at a friend's place I started to think it just was not going to happen, because the multiplayer component requires a Runic account to join their online game matchmaking service and a lot of GOG'ers would have a heart attack about that I imagine. Not sure if it has any other requirements that would be GOG unfriendly or not, but it's a great game either way and comes on sale for as low as $4.99 from time to time on Steam and various resellers.
zaine-h: But it isn't unprecedented. The same could be said Rise of the Triad, whose multiplayer also requires an account with the developer. If we ever saw it, the game would most likely be in the format of "Single Player works out of the box, multiplayer requires valid key (provided)" which is rather commonplace here. I'm okay with this as I'd only use single player anyway. Sure, some will complain. Some people just like to complain.
As I said, it has happened before but such times are very rare exceptions and not the general rule. There's no question of course that GOG.com would love to have a popular game like Torchlight 2 here, and almost certainly has been in contact with Runic about trying to make that happen. Runic ultimately holds all of the important cards though and they'd only consider doing it if they deemed it a worthwhile expense for the return on investment as I mentioned. That that hasn't happened suggests at least that they're either not interested or that it isn't a priority for them compared to other projects they likely have on the go.
Postal and Postal 2 - both games that are ancient by any standard now have had major updates in the last year or so and the first game's updates have made it to GOG with promises from the developer that the Postal 2 updates are on the way to GOG also. So this sort of thing does happen, but for every game like Postal or Postal 2 that does this, there are 500-1000 or more games that not only don't, but the majority of which wont. That's the sad truth.
All we have in the meantime is speculation at our disposal in lieu of official word from the developer, and most of them probably would rather not make official statements about such things to leave their options open and to avoid ruffling feathers if they make statements and change their minds later.
I've no problem with the license key requirement for multiplayer although I prefer without it, but a game like this is more likely the developer's requirements and choices not being met at GOG for them rather than GOG rejecting the game on some basis IMHO. Could be as simple as them wanting a single unified game experience for everyone playing the game rather than the Steam version, the GOG version, the xyz version, or it could be something else as simple as not wanting to commit resources to a game that's a couple years old with limited manpower allocated to other projects already. I'll bet the latter part is a big part of it. It's one thing to just release pre-existing binaries on a new digital platform, but a much larger and more costly proposition to redesign and re-engineer a part of a game for another platform.
I'm not justifying it mind you, just trying to put my mind in theirs to figure out what they likely feel about such from a business perspective where resources are finite and decisions are made on allocation of resources to the biggest bang for the buck. It would be great to hear someone from Runic actually make a statement though. I love their games and hope to see future games released on GOG.com also.