license of cstex / cslatex

[Thomas Esser <te@dbs.uni-hannover.de>]

Hi,

the teTeX package contains files which use the following license:

    COPYRIGHT
    =========

    This macro package (csplain.ini, il2code.tex, csfonts.tex, hyphen.lan,
    plaina4.tex) is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or (at
    your option) any later version with the following appendix:

    You can do any changes in this software for your own usage. However,
    you cannot distribute the changed software under the same name
    "csplain".  Only the current administrator of CSTeX can do official
    changes to csplain.

    This macro package 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.  See the GNU
    General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
    USA

I had done modifications of three files of that package and distributed
the changed files using the original filename. The author told me that
this violates his license. Actually, this only happened, because when
reading his license the first time, I stopped as soon as I saw a reference
to the GPL (and did not read the appendix).

Questions:
    - is it valid to refer to GPL and add such severe restrictions in
      an appendix?
    - is this a "free software" license in the FSF definition?
    - is this license free enough to allow an inclusion of the software
      into debian?

Regards,

Thomas Esser