ec¶

1. it refers to copyrite.txt (attached), which asks that any modified versions should be renamed to something different other than ec. (the name of the file is incorrect from the source) #969
2. it says that some files may be exempt from that copyright if expressly mentioned
3. no other files have such an exception (all have almost the same legend). I used this code to make the task easier (remove repeated lines to find those which had special notes):
   

   head -n 19 *.mf | grep -v '\(%[[:space:]]*$\|% (c) Copyright 1995, 1996, 1997 J"org Knappen\|% (c) Copyright 1996, 1997 J"org Knappen\|% This file is part of ecfonts version 1.0\|% Parameters for\|% European Computer Modern LaTeX Typewriter\|% (c) Copyright 1990, 1992 Norbert Schwarz\|% Please read the files 00readme.txt, 00inst.txt, 00error.txt, and\|% copyrite.txt for further information\|% You find some documentation in ecdoc.tex (needs LaTeX2e)\|% Content:\|%    Parameter for\|%    European Computer Modern Bold Extended Text Italic\)'
   

The only remarkable notes were for these files, but they do not seem affected by license issues in any way:

==> ecrb.mf <==
% ecrb.mf
% This file has been modified for local use by Tomas Vanhala 
% (vanhala@cc.helsinki.fi). (7-NOV-1994)
%          [ heavily borrowed from the Computer Modern Roman family of
%            fonts by D. E. Knuth ]

==> ecxc.mf <==
% ecxc.mf
% The parameters in this file were originally contributed by 
% Lars Engebretsen <enge@nada.kth.se> and Caj E. Svenson
% <atocasv@ato.abb.se>. 
% The two contributions were merged and retuned, if necessary.

==> exaccess.mf <==
% exaccess.mf
% Accessories and special definitions for polish letters
% Adapted to the ec fonts by J\"org Knappen
% Copyright (c) 1992 Bogus\l{}aw Jackowski \& Marek Ry\'cko
% Copyright (c) 1995, 1996, 1997 J\"org Knappen
% ---------------------------------------------------------------------------
% This was PL_DOD.MF ({\bif{}dodatkowy}, i.e., additional file for the Polish
% extension of CM family) in text format.
% ---------------------------------------------------------------------------
%%{\let\:\sl

==> exisixts.mf <==
% This is EXISIXTS.MF in text format, as of March 24, 1992
% ecfonts version 1.0
%          [ heavily borrowed from the Computer Modern Roman family of
%            fonts by D. E. Knuth ]
%   variant of 6test  modified for testing of ecfonts
%   should be used with exbase only

==> exsixtst.mf <==
% This is EXSIXTST.MF in text format, as of March 24, 1992
% ecfonts version 1.0
%          [ heavily borrowed from the Computer Modern Roman family of
%            fonts by D. E. Knuth ]
%   variant of 6test  modified for testing of ecfonts
%   should be used with exbase only

I already sent an e-mail to Gerd Neugebauer (gerd [lives at] informatik dot uni-koblenz dot de) to see if he wants to add a free license to PL.

cs¶

cs should be csfonts (download the sources from Arch and check one of the .mf files) and is free software (GPL)

mex¶

Free software should be readable, sharable and modifiable, so I don't think that "unchanged and complete form" qualifies (at best, it would be open source).