From Rosetta Code
GNAT GPL is an implementation of Ada. Other implementations of Ada.
GNAT GPL is part of GNU Compiler Collection. You may find other members of GNU Compiler Collection at Category:GNU Compiler Collection.

GNAT GPL edition refers to the versions of the GNAT Ada compiler licensed under the GNU Public License (GPL). Prior to 2005 GNAT was distributed under so-called GNAT-modified GPL license (GM GPL), which allowed the code compiled with GNAT and linked to its run-time library to be used commercially. All newer public releases of GNAT distributed by AdaCore are licensed under strict GPL. AdaCore continues to distribute GNAT under GM GPL, sold as a part of its commercial product GNAT Pro.