This is the README for GNAT 2.04 for Linux.

This package was compiled with the 2.04 source available from ftp://cs.nyu.edu.
You need gnat-2.04-linux.tar.  The bin tar contains the gnat* files for 
/usr/bin and the gnat1 that goes into /usr/lib/gcc* next to cc1.  The lib tar 
contains the Run Time Library and the adainclude directory as well as the 
README's and examples that come with the source.  You must untar these from / 
so that they will go into the proper places.
For example:

[boondock][/]# tar xzf /home/mcculley/gnat-2.04-linux.tar.gz

These binaries where built around gcc 2.6.3.  They will go into the gcc 2.6.3
directory.  These will probably work with gcc 2.6.2.  I have not tried.  If
you wish to use them with gcc 2.6.2, you will have to put the gnat1 bin into
/usr/lib/gcc-lib/i486-linux/2.6.2/ instead of 2.6.3.

This stuff has been minimally tested by myself.

Please remember that if you have problems with GNAT, you should write to the
GNAT team at gnat-report@cs.nyu.edu instead of posting to comp.lang.ada.
If you have any problems that are specific to these binaries or Linux, I can 
be reached at: mcculley@greatwall.cctt.com

Good Luck and Have Fun,
  Gene McCulley