I have created the C++ interface for using the GraspIt EigenGrasp planner without a GUI. The source can be found in the package grasp_planning_graspit. The results of the planning process can be saved as GraspIt world files and viewed in the original GraspIt simulator.
The GraspIt source is now a separate repository which is eventually meant to fork from a original source repository (if the developer is happy to move from svn to git). It is available in my repository graspit_ros. For now, it is just a fork of my own git repository which contains a 1:1 copy of the most recent source code I pulled from the original GraspIt svn repository. The package graspit_ros is a catkin package which can be used with catkin_make to compile a library and an executable of the original GraspIt simulator.
In the next few days I will keep working on the C++ interface and provide other means to get the results, including a ROS service. The next step is then to create an environment to test the grasps in Gazebo using the Jaco hand as an example.