Larian Studios Forums Divinity - Original Sin Divinity - Original Sin - General Divinity Original Sin on gamersgate?

Physical copies of games have to be ready some time before the release date, Larian was working on D:OS right up until launch, they didn't stop after the physical version went gold. The reason given for activation through Steam is so the game can be patched up to the current version immediately, and avoid the hassle of a buggy game.

D:OS:EE is going to GoG, so yes, the EE can be played without Steam.

Steam is not required to run D:OS. You could install D:OS through Steam, move the D:OS game folder elsewhere and uninstall Steam and D:OS would work fine.