HTC has released the kernel source and other GPL bits for the Desire S Gingerbread update, and for the various Sensation XL versions across the globe. As usual, average and well-adjusted people have no need for this, but for the true Android Geek and kernel developer, it's time to party. They can use these sources to further customize ROMs and streamline the kernel for better performance, which everyone loves. More importantly, it shows HTC is honoring their commitment and the terms they agreed to when using GPL software, which makes an old *nix nerd warm and fuzzy inside.
If you're in need of these sources, grab them at the link. If you're using a Desire S or Sensation XL, hang tight while the magicians do their magic now that they have the tools.
Source: HTC Developer Center