Brian Sniffen: >Thanks for the response -- I hadn't noticed that phrasing before. >But if I give *you* a copy of Sniffmacs under the Sniffen GPL, >wouldn't you then be bound only to give others the SGPL, not the GGPL >with its Preamble?
Now we get into a subtle point of copyright law. This is how I believe it works: If work B is a derivative work of work A, then to make a derivative work of work B (unless you carefully avoid all the parts derived from work A), you need licenses granted by the copyright holders of work B and work A. If Sniffmacs is work B and GNU emacs is work A, then in order to make a derivative of Sniffmacs, I need a license to work B (Sniffen GPL), which does not require preamble inclusion. But I also need a license to work A, and the license to work A specifies the inclusion of a copy of the GNU GPL. The GPL grants "you", the recipient, a separate license for each particular work. Term 6 is the term which propagates each individual license to the recipients of all modified works. Normally this sort of thing isn't an issue in free software. I only know about it because I looked at one point into the issues of making a sequel to a book which had characters used under license from two other books. (You have to get separate licenses from all three authors.) IANAL, of course....
