I took a quick look at this and I can reproduce the stack if I only add the helloworld directory to the Run Configuration classpath. It looks to me like the registry configuration is incorrect - it is bombing out looking for a TModel.
The sendesb target in the build.xml has exec-classpath as its classpath - exec-classpath is set in ../conf/base-build.xml. Since the ant target is working fine for me, I think the solution is to just reproduce the exec-classpath classpath exactly in Run Configuration.