BSD and MIT license "compliance" with the MS-PL

Matthew Flaschen matthew.flaschen at
Sat Apr 18 02:16:55 UTC 2009

Wilson, Andrew wrote:
> Matt, it does seem a little disingenuous to say one FSF citation is
> wrong (the one which explicitly calls MS-PL a copyleft license)
> and another is right (RMS's personal definition of copyleft, which
> is quite ideological and involves many tests that full freedom
> of the code is preserved).

Andy, of course it's ideological.  But it's not RMS's personal
definition, although he wrote it.  It's the FSF's definition, or it
would have been on not .  I think
it's disingenuous of you to imply otherwise.

Obviously their license list explicitly calls it copyleft, but as I said
I don't think that's consistent with the FSF's permanent definition ,
which undoubtedly they  consider far more important than a single
license entry.

> My personal definition of copyleft, for what it might be worth, as
> a term of art in open source licensing as opposed to the RMS ideological sense,
> is that copyleft is one step removed from permissive.

Copyleft without ideology is like a fire without warmth.  It was always
intended to be a highly ideological term, and as you know it was
popularized /by/ RMS.  So it's fairly ridiculous to now demand a
non-ideological definition.

> A permissive license allows derivatives to be sublicensed under terms and conditions of
> the licensee's choice.


> A copyleft license does not.

True, but that's not /all/ copyleft means.  Necessary but not sufficient.

>  A copyleft license says the only valid source license for derivatives is the original license.

Also true (as a consequence), but that's again secondary and not sufficient.

> MS-PL is sui generis because it is copyleft (under my definition
> above)

It seems your definition of copyleft is essentially, /It's not
permissive and it requires source code stay under the original license/.
 However, as you know that definition is inconsistent with the FSF's.
Moreover, it doesn't have any /purpose/.  Everyone knows the purpose
behind permissive and proprietary licenses, but what would be the
purpose behind your "copyleft".

Matt Flaschen

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