Playing online requires you to sign up for a account but the singleplayer and LAN play don't even need that. They're free indefinitely, not for a short window. You can grab StarCraft free for Windows here and for Mac here. But for now, free StarCraft for all is just dandy, ta. The real overhaul is coming later this summer in the not-free StarCraft Remastered. The game that birthed modern digital sports! The game that launched a thousand zerg rushes! The game that still has the best tanks in all RTSland! Blizzard have updated StarCraft a touch to play nicer with modern computers but mostly it's still just StarCraft ('just StarCraft' she says!). Blizzard's seminal 1998 strategy game StarCraft and its expansion, Brood War, are now free for all and sundry.