DokuWiki is a simple to use Wiki aimed at a small companies documentation needs. (GPL)
Cross-platform
Foswiki is a wiki, so you and your team members can collaborate and edit pages directly in the web browser. For advanced collaboration, Foswiki lets you enter macros to automate pages and build entire applications from within your browser. (GPL)
Cross-platform
MediaWiki is a free software wiki package originally written for Wikipedia. (GPL)
Cross-platform
mobiki is a small open source wiki engine implemented as one PHP file. It is optimized for usage with mobile devices with limited bandwidth and for fast HTML5 content delivery. (MIT)
Cross-platform
TiddlyWiki is a single html file which has all the characteristics of a wiki; including all of the content, the functionalityand the style sheet. (BSD)
Cross-platform
WackoWiki is a light and easy to install multilingual Wiki-engine. Supports WYTIWYG-editing, page rights (ACLs), design themes (skins), file upload, email notification and much more. Compatible with PHP7 and MariaDB / MySQL. (BSD)
Cross-platform
The XWiki project offers both a generic platform for developing collaborative applications using the wiki paradigm and products developed on top of it. (GPL)
Cross-platform
7 applications