Orbeon PresentationServer now features an improved source code viewer.
The viewer uses XForms to display the list of files with the Repeat module. It also uses an XForms submission to call a server-side formatting service which returns the content of the file marked up with HTML, either as a simple text version which preserves all the details of the original source file, or as an optional syntax-highlighted version for XML files.
Thanks to the Ajax-based XForms engine, the viewer allows you to navigate between files or change the viewing mode without the page ever reloading. It also has a "download" function which allows you to directly downlad a source file.
You can access the viewer by selecting the "View Source" tab of each example. It is also possible to link directly to a particular source file.