How to document "special" copyright cases (dual-licensing granted by upstream)

[Mathieu Trudel-Lapierre <mathieu.tl@gmail.com>]

Hi,

I've had one package (congruity) which has been rejected recently
because of a slight issue with one file not fully complying with the
DFSG (CC-BY-SA 2.5 rather than 3.0), and working on another (ethos)
for which the documentation would be non-free...

What is the proper way of reporting the fact that I've got upstream to
agree to dual-licensing of some files? Surely this information needs
to be documented somewhere in the package?

Sorry if this has already been discussed multiple times in the past.
I've done some searching, but for example the Reject FAQ doesn't seem
to say *how* to document such special cases.

Regards,

Mathieu Trudel
mathieu.tl@gmail.com