I am honestly surprised they aren't up yet, because the Discworld games are the type of games I would totally expect GOG to have. I hope it comes eventually.

As far as I know http://www.gog.com/forum/general/can_we_by_any_chance_request_games/post3 remains up to date.

I have a vague recollection that someone here tweeted Rhianna Pratchett about the games and got a vaguely positive reply, but I can't find that post if it exists.