Please CC me, I'm not on debian-legal email list.
I'm the Debian Developer for net-snmp. This package includes MIB files that translate human-readable SNMP parameters into numbers computers can understand. Sort of like a DNS hosts file for SNMP.
I'm not re-visiting the freeness or otherwise of the RFC documents themselves. Let's all agree that the license of the RFCs is still non-free as per .
Way back in 2008, a bug was put on net-snmp  saying that the MIB files used a non-free license. The offending MIB files based on RFCs were removed.
To use a specific example, the reasoning was we couldn't put, say SNMPv2-MIB.txt into net-snmp in main because they have in that file:
Copyright (C) The Internet Society (2002). This
version of this MIB module is part of RFC 3418;
see the RFC itself for full legal notices.
which leads us to the problematic RFC license.
So, what's different?
In 2010 IETF produced their "Copyright Policy and Trust Legal Provisions (TLP) Frequently Asked Questions" which (section 3) states Code Components are licensed under the Simplified BSD license if produced after 10 November 2008. Code Components between March 2005 to 10 November 2008 are licensed under something found in 3.3.C in RFC 3978 
The License to Code components (for items post-November 2008) is found at 
Code Components are defined at  and include MIB files.
I think what this all means is:
* MIB files created from RFCs pre-dating March 2005 are still a problem unless the RFC itself has some sort of copyright fix. e.g. no happiness for SNMPv2-MIB.txt which is before that date.
* MIB files created from RFCs dated March 2005 to 10 November 2008 might be OK, depending on what people think of the clauses in 3.3.C in RFC 3978
* MIB files created from RFCs after 10 November 2008 are licensed as Simplified BSD and (assuming the RFC itself has no special restrictions for its code components) can go in main.
I'd like that confirmed by the group here. I think a nice summary could go on the wiki at  for MIBS and everything else listed at .