With GNAT GPL 2013, AdaCore have extracted internal compiler components into a library called gnat_util, which is used by (at least) ASIS and GNATColl.
GNAT Util GPL 2013 contains components from the GNAT GPL 2013 compiler.
At least for ASIS, the components used to build it must match the components in the compiler, so if building ASIS for use with (for example) FSF GCC 4.8.0 a version of GNAT Util is needed which contains components from FSF GCC 4.8.0.
This project provides...