License compatibility of MS-PL and MS-CL (Was: (RE: Groklaw's OSI item (was: When will CPAL actually be _used_?))

John Cowan cowan at
Thu Aug 23 12:54:07 UTC 2007

Michael R. Bernstein scripsit:

> No, let me amend that: It bothers me that these licenses are
> incompatible with the entire universe of all other theoretically
> possible licenses, including future ones, regardless of their terms.

What you say is not *false*, technically, but it's highly misleading.

It is true that you can't take code licensed under the MS-PL and place
any other license on it directly.  However, it is still possible to make
a derivative work that incorporates MS-PL licensed code (by clause 2A).
Since you are the copyright owner of this derivative work, you may license
it under any terms you like that do not actually contradict the terms of
the MS-PL; that lets out the GPLv2 because of the patent peace clause (3B),
but allows many other licenses from Apache 2.0 to BSD to proprietary.

(I'd like to see a proper analysis of whether 3B conflicts with the
GPLv3's rules on additional terms.)

Furthermore, you may make a collective work incorporating the MS-PL
licensed code, since 2A also grants you the right of verbatim copying,
which is all you need for a collective work.

That, it seems to me, is all you could possibly want in practice.

> It also bothers me that this incompatibility extends not just to code
> mixing and sublicensing, but also to multiple licensing. Multiple
> licensing, like forking, is an unfortunate and infrequent necessity that
> I don't think should be given up lightly.

The normal multiple license issued by the copyright owner (whether
of an original or a derivative work) is disjunctive: that is, the
licensee may apply the terms of license A or of license B at his option.
The fact that licenses A and B contradict each other is no impediment.
For example, I license some code of mine under the GPLv2, the Apache 2.0,
and the AFL 3.0 licenses: you may apply whichever one you like.

The first thing you learn in a lawin' family    John Cowan
is that there ain't no definite answers         cowan at
to anything.  --Calpurnia in To Kill A Mockingbird

More information about the License-discuss mailing list