It’s the handiwork of Koush, who had to compile a Tegra 2 compatible kernel from third-party sources – since Motorola hasn’t released the XOOM kernel yet – and then figure out a root from that. Now it’s a relatively straightforward 15 step process.
He also took the time to build a recovery for the XOOM, but thanks to the non-functioning microSD card slot, which is waiting on a firmware update to enable it, it’s not been made public yet. Now, let the Honeycomb hacking begin.