I would just like to note that while it may be
"silly" or "useless"
to
insert licenses into minified JavaScript, it is nonetheless *legally
required* to do so, regardless of the technical aspect of it.
My 2 points - during my own research about free licenses, I've decided
that for JS, a good license is MPL 2.0:
http://www.mozilla.org/MPL/2.0/
Its advantages are:
1) It's "strong file-level copyleft". "File-level" is good for JS,
because it eliminates any problems of deciding whether a *.js file is or
is not a part of a derivative work, and any problems of using together
with differently licensed JS.
2) It's explicitly compatible with GPLv2+, LGPLv2.1+ or AGPLv3+.
Incompatibility problem of MPL 1.1 caused triple licensing of Firefox
(GPL/LGPL/MPL).
3) It does not require you to include long notices into every file. You
only "must inform recipients that the Source Code Form of the Covered
Software is governed by the terms of this License, and how they can
obtain a copy of this License". You may even not include any notice in
files themselves provided that you include it in some place "where a
recipient would be likely to look for such a notice".
Also, what I've understood also was that CC-BY-SA is not good for
source code at all, at least because it's incompatible with GPL. So
CC-BY-SA licensed JS may be a problem.