mingw-w64: Vague permission grant for embedded Cephes math lib

Hi,

The mingw-w64 package is a compiler and runtime library, that includes 
math functions copyrighted by Stephen L. Moshier. The license text 
contains this blurb [1]:

     FIXME: Cephes math lib
     Copyright (C) 1984-1998 Stephen L. Moshier

     It sounds vague, but as to be found at
<http://lists.debian.org/debian-legal/2004/12/msg00295.html>, it gives an
     impression that the author could be willing to give an explicit
     permission to distribute those files e.g. under a BSD style license. So
     probably there is no problem here, although it could be good to get a
     permission from the author and then add a license into the Cephes files
     in MinGW runtime. At least on follow-up it is marked that debian 
sees the
     version a-like BSD one. As MinGW.org (where those cephes parts are 
coming
     from) distributes them now over 6 years, it should be fine.

I believe mingw-w64 is extremely widely used and this package is almost 
certainly dfsg-free. However, I'm having a difficult time explaining 
that to a lawyer. Upon inspection of this paragraph, this seems like a 
weak justification and nothing like what is considered a modern license 
grant. The linked thread also does not really make a convincing argument.

I asked upstream[2] but didn't make much progress yet.

Dear debian-legal, do you have any advice on what grounds can this 
package be considered free software?

Thanks for your time, and apologies in advance if this is the wrong 
communication channel,

Regards
mappu

1. 
https://salsa.debian.org/mingw-w64-team/mingw-w64/-/blob/master/COPYING.MinGW-w64-runtime/COPYING.MinGW-w64-runtime.txt?ref_type=heads#L209 


2. https://github.com/mingw-w64/mingw-w64/issues/64