To
my knowledge, ghostscript does not contain non free files anymore.
Difference between ghostscript from Arch repos and ghostscript-libre
is only one file:
"/usr/share/ghostscript/9.10/Resource/CMap/Identity-UTF16-H", for which I
also think is free. Header of this file says:

% Copyright (C) 2003 Artifex Software.  All rights reserved.
%
% This software is provided AS-IS with no warranty, either express or
% implied.
%
% This software is distributed under license and may not be copied,
% modified or distributed except as expressly authorized under the terms
% of the license contained in the file LICENSE in this distribution.
...

So I've checked the ghostscript LICENSE file and found this:

The files in the Resource directory and any subdirectories thereof
are also part of GPL Ghostscript, with the explicit exception of
the files in the CMap subdirectory (except "Identity-UTF16-H",
which is part of GPL Ghostscript). The CMap files are copyright
Adobe Systems Incorporated and covered by a separate, Affero GPL
compatible license.

From what I see here, ghostscript is free, and there is no need for
ghostscript-libre.