For Approval: Microsoft Permissive License

Michael R. Bernstein michael at
Wed Aug 22 00:56:49 UTC 2007

On Sat, 2007-08-18 at 23:50 +0200, Nils Labugt wrote:
> lør, 18.08.2007 kl. 10.43 -0700, skrev Michael R. Bernstein:
> > From my POV, the fundamental difference here is *how* they choose to
> > exclude. Other pairwise license incompatibilities (including those that
> > involve the GPL) arise out of the side-effects of incompatible terms (in
> > the GPL's case, 'no other restrictions'), which at least leaves the door
> > open for pairwise combinations that are compatible.
> > 
> > In contrast, the MS-PL and MS-CL, by virtue of explicitly excluding
> > other licenses wholesale (including each other!), seem to have license
> > incompatibility as a *design goal* rather than a side-effect, and it is
> > *that* which I am very uncomfortable with. 
> For comparison, first from MS-PL: 
> "(D) If you distribute any portion of the software in source code form,
> you may do so only under this license by including a complete copy of
> this license with your distribution."
> [snip excerpts from two other licenses]
> Comparing these excerpts, I don't see why it is a "design goal" in the
> case of the MS-PL but only a side-effect in the other two cases.

This ignores the role of the word 'only'. This means that MS-PL is
incompatible with every other license, even the BSD license. That's a
bit different than being incompatible with some other licenses due to
conflicting requirements.

> > Not to mention eliminating
> > the possibility of dual licensing.
> If the license file and every source file states in no uncertain terms
> that the program is dual licensed, then I would be surprised if a judge
> lets the language "only under this license" in the MS-PL override that.

This is one of those situations where 'Microsoft has more lawyers than
me' comes into play. If I got an opinion to that effect from the SFLC
and a guarantee of pro-bono representation, *maybe* I'd consider testing
this, but frankly I think I'm unlikely to get either.

- Michael R. Bernstein
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