Info-ZIP's Zip 3.0: generic C sources.
  Complete C source code for Info-ZIP's
  PKZIP-compatible .zip archiver, for
  all supported compilers and platforms
  (Unix, OS/2, MS-DOS, NT, VMS, Amiga,
  Atari, Mac, Acorn, VM/CMS, etc.), plus
  lots of pretty decent documentation.
  Includes Info-ZIP's ZCrypt 2.9 for
  PKWARE-compatible standard encryption
  and decryption support for Info-ZIP's
  Zip 2.32, Zip 3.0, UnZip 5.52,
  UnZip 6.0, and WiZ 5.02 (and later).
This is FREE (but copyrighted) software.
See LICENSE for details on distribution
and reuse.