PraetorianWolfie: There's a free DLC announced for the game (over on Steam) that is to be released on November 18 (in about two weeks time). The tentative(?) title for the DLC is "Repentance+ Beta" and it will include online support as well as updates for the single player (I think mostly rebalancing stuff that players apparently were asking for, but probably bug fixes too).
Perhaps if / when the update eventually comes to GOG the game will be finally on the same level (minus the dailies but perhaps with a way to still acquire the items that normally are achieved via the daily challenges).
As the "Beta" in the DLC title implies. there probably be a follow up of more updates to bring it to a final state. Probably.
Neither GOG nor Nicalis have actually written anything about updates and free DLCs coming here though, and as far as I know noone has officially responded here on questions (about the potentially missing achievements/items and the lack of updates).
Oh this is news to me though given Nicalis track record of dumping games here with as far as I can tell little to no updates(I admit I own six of the games Nicalis put on here) I bet the dlc if it comes to Gog will only be after varies bug fixs and such the steam game gets from the dlc added to not have to support multiple platforms with updates at the same time