This is a great script idea and I would imagine not be hard to use/convert the idea to Maya and its animation layers as well.
I know several game teams and myself included that could have used this for either creation or just pre-viz of the additive animation work needed for the game engine.
From the Readme
"This creates an additive animation to be used on real-time engines, where the animation is to be "added" over another playing animation. You shouldn't actually subtract one animation from the other, but a "pose" (on Take02) from the animation on Take01."