NW writes "In a recent message to the MARID list RMS weighs in on the licensing issues of Sender-ID/SPF and Microsoft: 'Microsoft's Sender-ID license is directly incompatible with free software regardless of which free software license is used. Free software means users are free to run it, study and modify the source, and to redistribute it with or without changes. Free to do so means there is no requirement to ask or tell anyone that you are doing so.'" "MARID" stands for MTA Authorization Records in DNS; here's the IETF MARID working group's charter. (Read more below.)
http://slashdot.org/article.pl?sid=04/07/25/1343228