Not too long ago, Matthias Klose submitted an enormous patch (1370 lines) to python-mode.el (only 3804 lines itself):
https://sourceforge.net/tracker/index.php?func=detail&aid=875596&group_id=86916&atid=581351
I decided to start disecting it today and immediately ran into this comment by Dave Love (fx@gnu.org):
;; This file contains significant bits of GPL'd code, so it must be ;; under the GPL. -- fx
During the python-mode project's short life, I've copied python-mode.el over to the Python project's Misc directory a few times. I thought I'd better ask if GPL-ness would present a problem. I have always remained blissfully unaware of licensing details, so I have no grasp of what the ramifications are.
Serious. Do not copy this into Python. I would recomment rejecting the patch for python-mode.el as well (isn't that project also using the PSF license?). --Guido van Rossum (home page: http://www.python.org/~guido/)