We don't actually offer GNAT/PRO however it is listed here for completeness. GNAT Pro is the name of a product from AdaCore(approve sites). As we understand their product, GNAT Pro is licensed under terms similar to that of GNAT/GCC in that the core compiler is GPL while the Ada run-time is licensed under the GMGPL. AdaCore provides support services for GNAT Pro.
As is typically the case with most vendors that leverage open source software, it should be assumed that (with the possible exception of the GNAT/GPL edition) no version of GNAT Pro is identical to any of the releases we provide here since these releases are based on the release cycle of the Free Software Foundation (FSF) GCC tree which has different goals than that of a commercial company.