Failed to execute goal org.apache.rat:apache-rat-plugin:0.8:check (default) on project giraph-gora: Too many unapproved licenses: 56
There must be a file created by Apache Rat in the path giraph-gora/target/rat.txt (as this is the failed project). This file will contain details on the files in your projects that do not have a proper licence (as well as the ones that do but these are not of any interest to you).
Most likely, the case is that the files produced by eclipse (.classpath, .project, org.eclipse.core.resources.prefs, org.eclipse.m2e.core.prefs,org.eclipse.jdt.core.prefs) are creating the problem. If you remove them you will be able to compile giraph properly.