This research paper was published in 2000 at the IEEE International Conference on Robotics and Automation. Why did Sony allow this work, yet recently take action to stop other amateur modifications of the Aibo robot?

"An evolutionary algorithm is used to evolve gaits with the Sony entertainment robot, AIBO. All processing is handled by the robot's on-board computer with individuals evaluated using the robot's hardware. By sculpting the experimental environment, we increase robustness to different surface types and different AIBOs. Evolved gaits are faster than those created by hand. Using this technique we evolve a gait used in the consumer version of AIBO. "

Also check out the following paper, published in the proceedings of the 1999 Genetic and Evolutionary Computation Conference.

Autonomous Evolution of Gaits with the Sony Quadruped Robot
http://www.demo.cs.brandeis.edu:80/papers/hornby_gecco99_sony.pdf

"In this paper we report our results of autonomous evolution of dynamic gaits for the Sony Quadruped Robot."

Sony's selective enforcement on Aibo modifications?