That's correct, there is currently no keyboard compatibility. The reason for this is that most keyboards have a limit on simultaneous key presses which means that inputs get dropped when 3+ non-modifier keys are being held at the same time.
As a two player game that requires 3-4 buttons per player, it's simply not possible for us to provide a control scheme that will allow a consistent and fair game on a single keyboard. We WILL add limited keyboard support in the future for use in the single player modes and likely allow for a mixed input option for multiplayer (as in, one player can use the keyboard while the other player uses a gamepad), but it's unlikely that we will ever allow two players to play on the same keyboard.
-Eric, Virtually Competent Team Lead