Apache JServSSI Project - Describes the predecessor to JSP technology; includes syntax and distribution. [Open Source, BSD-like] - http://archive.apache.org/dist/java/
Tea - A simple yet powerful template language. Tea is most commonly used for creating dynamic web pages in the TeaServlet. [Open Source, Apache-like] - http://teatrove.sourceforge.net/tea.html
FreeMarker - Java template engine; a generic tool to generate text output (HTML, RTF, and source code) based on templates. Particularly practical for servlet-based Web applications following the MVC pattern. [Open-source, BSD-style] - http://freemarker.org/
WebMacro Servlet Framework - A server-side scripting engine. It uses Java introspection to make any object in your servlet accessible in your scripted template. [Open Source, GPL/Commercial] - http://www.webmacro.org/
The Rich Mens Document Management System (rm -d ms) - XML/XSL based document management system designed for running websites. Server side application logic is implemented by XSL stylesheets, which may call hard-coded components. [Open Source, GPL] - http://rmdms.sourceforge.net/