real.geizterfahr: The X Superbox is completely DRM free* and contains X: Beyond the Frontier, X-Tension, X2, X3 Reunion and X3 Terran Conflict.
*The Superbox comes with an activation key to register the game on Egosoft's website, but that's 100% optional. And I think when Albion Prelude came out, they made this key Steam redeemable. But I'm not sure about that. However, the two X3 titles are available DRM free in the Superbox.
edit: Just saw this was already discussed... Note to myself: Read first, answer afterwards xP
But it's still tied to a DVD right? It's not a downloadable thing?
darkwolf777: You might check the Humble Store, I know they had a bundle a few months ago with most of the X games which I'm pretty sure were DRM free but also came with Steam keys if you wanted to activated them on Steam as well.
Holy cow, that is promising. Can't believe I missed that. Guess I'll be checking the Humble Store every once in a while then.
Gmr_Leon: I guess not, in terms of purely digital. =/ However, you do get a DRM-free installer in the form of the disc, which is pretty decent in my book. Not ideal, maybe, but at least it's a local backup in the event of company shutdown/server failures.
Until the DVD breaks, get stolen or my house burns down, though I suppose the later 2 would apply for backups on external drives too (unless I stored them at different places entirely).
Also, my DVD game collection was getting a bit out of hand in terms of storage. Not sure I'd want to go back to that.