Currently libc0.1 is the official glibc version for the hurd in the main archive. I suggest that you do your research a bit better; or maybe the Debian GNU/*BSD people should make it clearer, the naming of the package isn't exactly wonderful. libc0.1 is a Debian GNU/*BSD package, it isn't even available on Debian GNU/Hurd. Debian GNU/Hurd uses libc0.3 since ~2000, before it used libc0.2, and before _that_ Debian GNU/Hurd didn't exist.