The configure script in input-wacom-0.30.1 indicates that it might be possible to compile the driver for kernels as early as 2.6.26. Building anything prior to 2.6.30 fails, however, since several definitions (BTN_TOOL_QUADTAP, ABS_MT_POSITION_X, and ABS_MT_POSITION_Y) are not present.
Fixed by 3ba6e72
Fixed in 0.30.2