FLUID: Echo is a very nice looking concept for a CollaborativeAuthoring system similar to a Wiki that allows the creation of custom properties/attributes and tracks change history at the annotation level.  It is possible that all that currently exists for this project are a few papers since there don't seem to be any project links to be found.

Links:
* http://wwwbruegge.in.tum.de/pub/Lehrstuhl/DesignRationaleSoSe2004/ECHO-MSEC2003-final.pdf
* http://venus.cs.depaul.edu/xjia/tefse03.pdf

-- SteveJorgensen