Hmmm... what could it be...
Lucas Arts have their games on Direct2Drive, while their customers are crying for the games on GOG.
http://lucasartsworkshop.wordpress.com/about/
The space theme hint could perhaps be refering to The Dig? They have already tested the water by releasing the games on D2D, so maybe they figured its time submit to the customers demand.
Firaxis / 2K Games released Civilization 4 The Complete Edition without DRM protection, and they previously released Civilization Chronicles with the Civilization 1 - 4. Seemes like they have the rights to sell their old games, so maybe? We have the Space Race in Civilization, and the Alpha Centaury game which could correspond to the hint on the main page. And lets face it, Civilization is perfection!
The old Sierra games got re-released, so maybe its the Space Quest series?
At some point, I think Lucas Arts, Firaxis / 2K Games (old Microprose games) and Sierra games will be found on GOG. But for now, my guess is on Firaxis as I dont think they have such a rigid view on DRM.