A forum post by the GOG.com team announces the etailer is stepping up and offering refunds for Dark Matter for those who feel deceived by the game's description, which they have changed (thanks PC Gamer). Here's word:

It's come to our attention that the gamecard for Dark Matter was not quite specific enough about the nature of the game and, as a result, it may be that some people bought the title with some misapprehensions as to how the game's story would end. Since we don't ever want to sell a game to someone because they believe it is something that it is not, we wanted to let you know about this and let you know what we're doing to make it right.

If you bought Dark Matter before 21 October 2013 at 15:00 GMT (when we updated the description to where we feel it adequately reflects the game) and you feel that the game wasn't as promised to you, please contact Support and they'll be happy to offer you full refund to your card or, if you''d prefer, games of equal or lesser value to the sale price of Dark Matter (which is $13.49).

We're sorry if anyone who bought the game isn't happy with the way it was represented, and we hope this makes it right for you guys.

If you've got any questions, hit me up and I'll try to answer 'em for you.