I created a repository that will contain my new packages:

rosinstall ~/ros /opt/ros/groovy/
echo "source ~/ros/setup.bash" >> ~/.bashrc 
source .bashrc

Do a checkout manually of the sources:

svn co https://svn.code.sf.net/p/bosch-ros-pkg/code/trunk/stacks/exploration ~/ros/exploration

There is an broken link to btVector3 in the following file: ~/ros/exploration/explore/include/explore/explore_frontier.h

Just change the line

#include <LinearMath/btVector3.h>

to

#include <tf2/LinearMath/btVector3.h>

Then you can build the project:

rosmake exploration

Before running explore, launch turtlebot and gmapping:

roslaunch turtlebot_bringup turtlebot.launch
roslaunch turtlebot_navigation gmapping_demo.launch

To run the explore node, run this command line:

roslaunch ~/ros/exploration/explore_stage/explore.xml