Wolfgang Denk [mailto:wd@...]:

But this example doesn't work either. If you mix a license that allows "modify and keep the modified code closed" with GPL, the only legally possible result is GPLed code.
I see little value in constructing such more or less artificial examples.

This is not artificial. Here's code that I wrote:
http://sourceforge.net/p/readable/code/ci/master/tree/src/sweet-clisp

Note this comment:
# Except as otherwise marked, this code is licensed under the "MIT license".
# However, the "override" code that patches clisp is derived
# from clisp, which is GPLv2.
# Thus consider the work as a whole as "MIT and GPLv2".

I agree with you that, from a *legal* standpoint, if you accept the WHOLE file you end up with just the GPLv2 requirements. But knowing that there's a variance matters; it's quite possible to extract a part and end up with just the MIT portions.

This one file is part of a larger system that is mostly MIT, but has this one GPLv2 file. Claiming it's just "GPLv2" would be very misleading. Being able to report the options, collected with AND and OR, is very helpful.

--- David A. Wheeler