It is an implementation of JSPWiki http://www.jspwiki.org/ for Google App Engine.
Current implementation (first draft) is available http://testjspwiki.appspot.com/ Warning: it could take a minute or more before wiki starts
Source code is available - go to Source tab. Unfortunately, I found impossible to keep backward source compatibility with the main JSPWiki stream so it will be developed as different trunk.
It is the very first version and can be changed in the future.