A wiki/ CMS dedicated to multilingual contents.

A free wiki engine written in PHP and MySQL available under the GPL. Site contains source code and documentation.

Wikipedia's underlying open source wiki engine.

Feature-rich implementation with support for various databases.

A simple-to-install system which allows password protection and organization of pages into groups (GPL).

Popular extension of Wikipedia's wiki engine with Semantic Web features, enabling better search and organization of wiki content.

Free, libre, open source web application platform with an article system, blogs, forums, file and image galleries, chat, calendars and events. WYSIWYG editing.

Small, lightweight, handy, expandable, multilingual Wiki-engine based on Wakka Wiki. WYSIWYG editor, easy installer, many localizations, email notification on changes/comments, several cache levels, design themes (skins) support, XHTML compliance, page rights (ACLs), page comments.

An AJAX based wiki engine designed to operate similar to a desktop help viewer.

A free PHP/ MySQL wiki engine based on forked code from WakkaWiki. Includes a GUI page editor, advanced syntax highlighting and mindmap support. Released under GPL.