Larian Studios Forums Divinity - Original Sin Divinity - Original Sin - General Steam and Original Sin's FAQ

Gonchi
Yes, if Larian knew at the time the retail version would be Steam, they should have been clear about that, and they could have been explicit when announcing the CE (though I don't know how many retail versions come with Steam keys and have a separate, non-Steam version on disk).
Likewise, if you've seen so many people throw around terms that they don't understand that you are tired of this situation, you could have explicitly asked if the retail version was Steam.