"You will still have to be logged on for the individual campaign, which features new functions online, but those parts which have no reason to be connected are still available offline, such as editors, LAN, splitscreen or Hotseat mode.
Maniaplanet is a system of networked games like web 2.0, and as such, it is unnecessary to include a DRM. It's been like that for the last five years with TrackMania which has already sold many copies." - Hylis from Nadeo.
I have purchased and played TM2: Canyon, and it's excellent. The system is set up much like TM: Nations Forever and TM: United Forever were. When you first get the game, you set up an account and verify your activation key. After that, you can play offline if you choose (a friend verified this one for me by turning off his network connection and starting up the game). You won't get access to some of the online features (earning "planets" - similar to coppers in Nations/United from what I understand) and obviously can't play online multiplayer, but you can play. Personally, I'm just glad Ubisoft pretty much left Nadeo alone for this one, especially after I got suckered into From Dust (Glad I got my refund today from Steam, though).