Glass is running a version of Android, so it's packing the Linux kernel as wellGoogle Glass is still a year away from being put on sale, but it's constantly getting some attention, just like Google wants it.
While regular folks won't be seeing Glass any time soon, developers have been able to get their hands on the device for a while.
A short while ago, the first jailbreak for the device was made available, indicating that developers were already tinkering with the device and its inner workings.
And that's how Google wants it, not necessarily because it's so open, but because it knows Glass' success hinges on the applications that are available for it.
So now, it's releasing the entire Glass kernel code as open source. Considering that Glass is essentially running Android and that Android relies on the Linux kernel, the fact that the source code for the kernel is available shouldn't be surprising, it's a requirement of the kernel license.
Still, Google could have waited until Glass was out or even longer before releasing the code. For now, the code is available at a temporary location, before it gets merged with the regular Android kernel code.