If you want to play the multiplayer maps against AI, do the following:

Open the install directory of Dungeon Keeper, something like

Find and open
in your text editor.

Go to line 40 and replace
with
in order to activate skirmish mode in Dungeon Keeper.

Go to line 46 and replace
with
in order to activate skirmish mode in Deeper Dungeons.

Now you just start the game, select "Multiplayer", and then "1 Player".