So the school district need only prove that ID is not creationism to win the case? If that's true then I think the ACLU has badly miscalculated.
Actually no. That's sort of a mis-statement of what issues the case will look at. The actual inquiry will be whether the actions of the Dover School Board in implementing their "intelligent design policy" were done with (1) a religious purpose, that (2) advances religion, possibly resulting in (3) government entanglement with religion.
Whether other people's version of ID is religious in nature is ultimately irrelevant to what the Dover Board believed.