You're right. I wasn't aware of the libc5 to glibc 2 transition, it predates my first Linux usage, too. I have found by the way that while Ubuntu does not offer a lib5 version, Debian does. But there's no way to get a compatible xlib version, you need a specially patched one. The point is: no binary compatibility, you need to build your own base libraries. While I'm not sure, I'm pretty confident I could install WP8 on Windows without much hassle, even today.