In case you've missed it, the firmware for the microcontroller is now on GitHub: https://github.com/samp20/SelfBalanceSkateboard

As of this post there's no support for steering yet, however I have implemented a PD loop for balancing. I can't really do much testing at the moment anyway until I have a proper enclosure for the electronics. I'm going for a steampunk-ish theme, so stay tuned.