I would like to offer ESRI a full function CAD program which was developed for an architectural firm and now its source code is open source. It was a serious competitor to AutoCAD in the late 80's and early 90's (but lost). Recently, it was updated through a grant from the IMLS and will compile on Visual Studio 2010. It was used in a spatio-temporal cultural heritage project for visualizing city development over time. We're finished with the project and the source code is available (400,000+ lines of C++).