AdaCore's compilers are lawyerbombed; they're GPL'd without the library exception, so you can't use it for non-GPL'd software. (The binaries are unreleasable due to license conflict.)

It's actually freeer to download the FSF-distributed version, which is GPL'd with the library extension. See: http://www.getadanow.com/

The FSF version is usually a couple of minor releases behind the AdaCore version, but is otherwise much less hassle.