seems to be public domain now (at least the versions in Debian) http://metadata.ftp-master.debian.org/changelogs/main/z/zoo/unstable_copyright
I changed the LICENSE in zoo-2.10-r5. The program still announces that it's copyrighted as part of the "help" output, but that will have to be patched out. I'll leave myself a note to stabilize and clean up some time in the future, and at that point I'll check to see if the "zoo" license can go.