From gog.com's promo page:
We're celebrating the one-year anniversary of our Early Access Beta launch with a rerun of our "Buy 1, Get 1 Free" Interplay promo! From now until Tuesday, September 8 at 11:59 p.m. EDT you can buy any game from the Interplay catalogue and get another absolutely free! To take advantage of the promo just select the games you want from the list above. You have to place order on games in pairs ex. two, four… ten games in one order, to get half of them for free.
All games are $5.99 USD, here's the list:
FALLOUT $5.99
FREESPACE 2 $5.99
GIANTS: CITIZEN KABUTO $5.99
SACRIFICE $5.99
REDNECK RAMPAGE COLLECTION $5.99
DESCENT 3 + EXPANSION $5.99
FALLOUT 2 $5.99
FALLOUT TACTICS $5.99
FREESPACE + EXPANSION $5.99
DESCENT + DESCENT 2 $5.99
EARTHWORM JIM 1 + 2 $5.99
MDK $5.99
Does anyone know the shipping charges?