https://www.dokuwiki.org/dokuwiki
Started 2004
Programming language: PHP
Backend: Filesystem
License: GPL
Started: 2016
Programming language: JS and Vue
Backend: PostgreSQL, MySQL
License: AGPL
Started: 2010
Code: https://github.com/gollum/gollum
WYSIWYG: no
Programming language: Ruby
Backend: git
Format: markdown and other
License: AGPL
Started: ...
Code: https://github.com/moinwiki/moin
WYSIWYG: no
Programming language: Python
License: GPL
Code: https://github.com/xwiki/xwiki-platform
License: LGPL
Programming Language: Java