MS-PL/GPL compatibility, was Re: For Approval: Microsoft Permissive License

Wilson, Andrew andrew.wilson at
Thu Aug 23 16:17:20 UTC 2007

Chris Travers wrote:
>On 8/23/07, Tobia Conforto <tobia.conforto at> wrote: 
>	Chris Travers wrote:
>	> Tobia Conforto wrote:
>	> > If I take a MS-PL file (not mine) and a GPL file, combine
them into
>	> > a derived work and release it as GPL, the GPL requires the
>	> > work (including the MS-PL part) to be released with
>	> > exactly equal to the GPL
>	>
>	> Read section 7 of the GPL v3 again, or section 2 of the GPL
>	> Additional permissions are not prohibited.  However the MS-PL
is not
>	> compatible with the GPL v2 on other grounds. 
>	>
>	> The GPL v3 also allows for reasonable legal notices to be
included, so
>	> the requirement that source code be identified as being still
>	> the MS-PL does not seem to be a problem.
>	You are right, I was reading the GPL wrong!  (It's so long...

Actually, Tobia, your original position is correct (at least it
is consistent with most people's reading of GPL, and other copyleft
licenses such as EPL and CDDL).  Copyleft licenses as a group all
insist that derivatives must be licensed under their terms and
conditions.  If they did not have this characeristic of license
"stickiness," it would be trivially easy to defeat the requirement
to share source, i.e., the reason people choose to apply copyleft
licenses in the first place, by purporting to relicense derived code
under a non-copyleft license.
Of course, it is exactly this property of license "stickiness" that
makes most copyleft licenses (I have to say IMO unfortunately)
with each other.

MS-PL is an odd duck in that it is a non-copyleft license with a
similar "license stickiness" clause which forbids relicensing.  
This makes it, too, incompatible with copyleft licenses.

Andy Wilson
Intel open source technology center

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