GNU readline
  
   Aladdin Ghostscript does not include an interface to GNU readline.
   Even though the GNU License (GPL) allows linking GPL'ed code (such as
   the GNU readline library package) with non-GPL'ed code (such as all
   the rest of Ghostscript) if one doesn't distribute the result, the
   Free Software Foundation, creators of the GPL, have told us that in
   their opinion, the GPL forbids distributing non-GPL'ed code that is
   merely intended to be linked with GPL'ed code. We understand that FSF
   takes this position in order to prevent the construction of software
   that is partly GPL'ed and partly not GPL'ed, even though the GPL does
   not in fact literally forbid this (it only forbids distribution of
   such software). We think that FSF's position is both legally
   questionable and harmful to users, but we do not have the resources to
   challenge it, especially since FSF's attorney apparently supports it.
   Therefore, even though we added a user-contributed interface to GNU
   readline in internal Aladdin Ghostscript version 5.71 and had it
   working in version 5.93 (the next-to-last beta version before the 6.0
   release), we have removed it from the Aladdin Ghostscript 6.0
   distribution.
   
   GNU Ghostscript distributions will include support for GNU readline.
   As with other GNU Ghostscript components that are not included in
   Aladdin Ghostscript, Aladdin will not attempt to run, link, or even
   compile this code, or keep it current across changes in the rest of
   Ghostscript. We will, however, welcome bug fixes or updates, and
   distribute them with subsequent releases of GNU Ghostscript.
   
   The first GNU Ghostscript distribution that will include GNU readline
   support will be GNU Ghostscript 6.0, currently scheduled for release
   in the third quarter of 2000. Before that time, we may return the
   copyright of Ghostscript's GNU readline interface module, which the
   original author assigned to Aladdin Enterprises, to the author, so
   that users of GNU Ghostscript will have have access to it. However,
   since it requires internal changes that are not and will not be
   available in any released GNU Ghostscript version before 6.0, any user
   who gets this code and links it with Aladdin Ghostscript 6.0 will,
   according to FSF, be violating the intent (though not the letter) of
   the GPL.
   
   We have, in fact, put considerable work into making it possible for
   Ghostscript to use GNU readline, including the creation and/or
   adjustment of internal software interfaces specifically to serve this
   purpose. In principle, we should have undone this work in Aladdin
   Ghostscript as well, lest FSF object to it too as intended to
   facilitate linking Aladdin Ghostscript with GNU readline (as the U.S.
   government has been said to do for code that merely provides APIs
   where encryption may be added). However, we are willing to take this
   risk rather than spend the time to undo the interface changes.
   
   If you have comments or questions about this situation, please feel
   free to contact the Free Software Foundation, authors of the GPL and
   copyright holders of GNU readline, at gnu@gnu.org, and/or Aladdin
   Enterprises, author and copyright holder of Ghostscript, at
   ghost@aladdin.com.