I've been trying to find the source code of the Linux kernel Sony uses on its PRS-T1 reader. From Sony's Open Source pages  , a search for “PRS-T1” leads to these two pages (for the non-Russian/Japanese versions):
The Linux tarballs distributed from these pages do not seem to correspond to the Linux trees actually used to build the kernel on the device, though: Comparing the device's /proc/config.gz with the options actually present in the distributed source code shows that various configuration options appear in the build, but not in the source code, and (less significantly) also vice versa. For example, the running kernel has set a configuration option CONFIG_READER_WIFI, which does not appear in the source code at all.
I'd be interested in the real Linux source code as used on the device. Is there another place to look for it? If there isn't, Sony may be in violation of the kernel's GPL license.