I am not sure if this will help, but evidently you can place various resources (e.g. javascript, css) into the "project skins" directory. By default forrest.properties this is at src/documentation/skins/$skin-name/ Javascript files would go in a "scripts" subdirectory. CSS files would go in a "css" subdirectory.
Then refer to those from your source documents with URIs like /skin/blah.js and /skin/foo.css I am figuring this out by looking at the core sitemap called forrest/main/webapp/resources.xmap Search for "javascript" then follow to the <map:resource name="skin-read"> section. Hope that helps. -David