Non-free files in source packages?

[Simon Josefsson <jas@extundo.com>]

Hi.  I'm not that familiar with the Debian policies, but I hope
someone here can explain something for me.

Are there any policies surrounding what may go into the source
packages, that Debian distribute, as far as license is concerned?

Do Debian consider it problematic if source packages include, say,
RFCs, which, if I understand correctly, are considered non-free by
Debian otherwise?

If not, what is the difference between distributing the RFCs in source
packages and in the base-system?  Perhaps RFCs can finally become part
of the base system, by distributing them as a source package?

Otherwise, how do Debian handle the situation when the RFC is parsed,
and become part of the implementation?  In other words, where the GPL
require that you distribute the RFC because it is the preferred
"source code" to make modifications to.

Thanks,
Simon