SPIP is a publishing system for the Internet in which great importance is attached to collaborative working, to multilingual environments, and to simplicity of use for web authors. It is free software, distributed under the GNU/GPL licence. This means that it can be used for any Internet site, whether personal or institutional, non-profit or commercial.
SPIP is developed (programmed, documented, translated, etc.) and used by a community in which there is an open invitation to participate. To do so, make contact through one of the various websites, mailing lists and meetings (aka. SPIP parties) which exist.
SPIP was born in 2001 at the initiative of "minirézo", a community defending freedom of expression on the Internet (see the article on uZine). Nowadays SPIP is used by tens of thousands of widely varying sites. This site contains the official documentation.