As of today, June 1st, 2017, The Game of the Year Deluxe Edition of The Elder Scrolls IV: Oblivion, the fourth game in The Elder Scrolls series, is available for purchase DRM-free on the GOG ("Good Old Games") store, which is a similar platform to Steam.
Oblivion is the sixth title in the series to be sold on GOG, alongside The Elder Scrolls: Arena (1994), The Elder Scrolls II: Daggerfall (1996) An Elder Scrolls Legend: Battlespire (1997), The Elder Scrolls Adventures: Redguard (1998), and The Elder Scrolls III: Morrowind (2002).
As the version on GOG is DRM-free, you do not require any sort of activation or internet connection whatsoever to play the game. This is not the case with most Steam games, in which you are simply borrowing the software from the developers and do not have full control over your copy.