Im not into the automation tools, i might start using them when i know how it works by hand.
Their libraries are small, and it "looks" like Kobo isnt compliant with GPL as the package is missing from their repo.

They havent used files from the toolchain either, those are way too big.
Its booting with their files, that presumably looking at their names are from glibc 2.11: ./ld-2.11.1.so, ./libc-2.11.1.so ..etc.
Slimmed down its about 4MB, KOReader adds another 65MB.