This RT extension (designed for RT 3.4.5 and newer) implements a per-ticket "Wiki" whiteboard field.

To install it, type:

   perl Makefile.PL
   make
   make install


The extension looks for a custom "wikitext" field called "Whiteboard" which applies to a
ticket being displayed. This way you can easily have different whiteboard fields with
different ACLs on different queues.