Open Source Java Wikis

... and Blogs with wikiing support:

Blogunity (GPL)
blojsom (BSD)
JSPWiki (LGPL)
Pebble (BSD)
SnipSnap (GPL)
VeryQuickWiki (LGPL)
yawiki (???)
XWiki (GPL)

Wiki Render Engine: Radeox (Apache 2.0)