See our http://forrest.apache.org/gump.html
The "forrest-core" has been building properly for some time now.
Also "forrest-test-basic" builds properly. It builds a simple site with no plugins, so just exercises the core of Forrest.
However the "forrest-test" has some strange issue finding the plugins. Follow the link to the "vmgump.a.o" reports. The nag emails are coming only to me at this stage.