Open Source and Freeware Libraries
Info-ZIP is an open working group providing compatible solutions to the former standard software pkzip and pkunzip. The C source code is licenced liberally equivalent to BSD. The freeware applications ZIP, UNZIP, WiZ and MacZip are created by the Info-ZIP members.
Development and maintenance: Ed Gordon, Mike White, Dirk Haase (and many others)
The freeware application bzip2 is based on LIBBZIP2. The ANSI-C library is licenced equivalent to BSD.
Development and maintenance: Julian Seward (and others)
LZMA (7-Zip, LZMA-SDK)
The LZMA-SDK (System Development Kit) provides the base for the standard compression method of 7-Zip. Two different licence models are available:
GNU Lesser General Public License (GNU LGPL)
Common Public License (CPL)
LZMA is derived from LZ77 and used with the 7z file format.
Development and maintenance: Igor Pavlov
ZLIB is a free library supporting data compression as described within RFC 1950 "ZLIB Compressed Data Format Specification". It is written in C and licenced very liberal.
Development and maintenance: Jean-loup Gailly, Mark Adler (and others)