The MARID Working Group of IETF (http://www.ietf.org/html.charters/marid-charter.html) is close to settle on its Sender-ID protocol. Microsoft claims patents on some parts of Sender-ID (http://www.imc.org/ietf-mxcomp/mail-archive/msg03495.html). Microsoft drafted a licence for those wishing to implement Sender-ID. I've found it small enough to be attached here but, otherwise, it is at http://www.imc.org/ietf-mxcomp/mail-archive/msg03496.html and has a FAQ at http://www.imc.org/ietf-mxcomp/mail-archive/msg03497.html. It is not common to have Microsoft licences in debian-legal :-) I do not send it here for a specific software but because the possibility of IETF standardizing a technology which depends on a patent with a non-free licence is worrying. I believe this licence is certainly GPL-incompatible and probably non-free. Other analyses of the licence: http://www.imc.org/ietf-mxcomp/mail-archive/msg03500.html and http://www.imc.org/ietf-mxcomp/mail-archive/msg03514.html.
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SenderID_License-Agreement.pdf
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