From Fedora Project Wiki

Licensing Notes

This license is considered Free, but GPL-incompatible only when used for TeX files. In all other use cases, this may not be true.

License Text

% psfrag.dtx Copyright (C) 1996 Craig Barratt, Michael C. Grant,
%                               and David Carlisle.
%            All rights are reserved.
%
%            This system is distributed in the hope that it will be
%            useful, but WITHOUT ANY WARRANTY; without even the
%            implied warranty of MERCHANTABILITY or FITNESS FOR A
%            PARTICULAR PURPOSE. Don't come complaining to us if you
%            modify this file and it doesn't work! If this file is
%            modified by anyone but the authors, those changes and
%            their authors must be explicitly stated HERE.