Any news for this?
Have the repository been changed like BPEL from CVS to SVN?
You should check out the branch branch_jbpm_jpdl_gpd_3_1_x to have the latest sources of the 3.1.x branch.
As for the new GPD 4, the sources are in the jboss tools svn. I'll write up a wiki article that describes how to get/build it.