@twobob/knc1: Yeah, the glibc's ABI backwards compatibility has been pretty solid, in my experience, without too much burden
. That's why your current binaries should work with the Kindle's newer glibc. (Keep in mind that glibc isn't only libc.so, though, there a whole bunch of other core library in there: libm, libcrypt and libdl being the most prominent of those).
For a stark comparison, libstdc++ is a whole different kettle of fish. There *is* ABI compatibility, but there have been so much change in the API over the years that you usually *need* to ship it/static link it to make sure it won't blow up, especially on older systems...
There's still a libstdc++-v3 package available in nearly every distro out there to provide support for older dynamically linked binary/proprietary C++ apps for this very reason.