JSPWiki tries to be rather developer-friendly.
The source code is available for you to download, and there are quite a few places where you can tweak the code.

• Online JavaDocs
• For all of the Wiki markup features, see TextFormattingRules.
• The Wiki.Developer.RPC Interface might interest you if you're into scripting.
• Wiki.About.Attachments - very useful things.
• Wiki.How To.Use Variables - putting things on top of other things.
• WikiPlugins - The documentation on plugins. See also DevelopingPlugins
• JSPWikiFAQ - A list of some frequently asked questions.
• JSPWikiTags - A list of tags for those who want to make their own Wiki.Developer.Templates.
• Wiki.Admin.Multiple Wikis - If you want to run multiple Wikis using the least amount of effort.
• Page aliases and redirecting.
• PageFilters - for more complex processing.
• Wiki.How To.Create Forms - for putting interactivity in your pages
• Wiki.Admin.URL Constructors - for constructing your URLs.
• ResourceRequests - A way to programmatically change the page output from plugins.
• Rendering - an explanation on how JSPWiki renders pages

StubArticle, RefactorMe