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

saulgoode at saulgoode at
Fri Apr 17 22:09:45 UTC 2009

Quoting Chuck Swiger <chuck at>:

> On Apr 17, 2009, at 11:40 AM, Wilson, Andrew wrote:
>> Back on the original topic, I don't see any reason to believe
>> BSD or MIT code could not be combined with MS-PL code.
> Also agreed.  From the original submission thread of the MS-PL license,
> by Jon Rosenberg of Microsoft:
> "* Can MS-PL code be redistributed in combination with other code
> that is licensed under a different license?
> As long as the original MS-PL licensed code is redistributed under
> the MS-PL license, then the MS-PL places no restrictions on
> combining MS-PL code with other code that is licensed under another
> license.  Licenses that prohibit the distribution of code under any
> terms other than the terms of that license will not be compatible
> with the MS-PL."

How is Mr Rosenberg's assertion supported by the wording of the  
license? *Copyright law* decides whether "combining" code results in a  
derivative or collective work, not a license (especially so if the  
license does not address the issue).

Unless there is language within the license addressing this issue, the  
author of the license has no say in whether the combination of code  
under disparate licenses should be considered to result in a derived,  
or even collective, work. This a determination made only by the  
holders of the code's copyrights (in that they may choose whether or  
not to litigate infringement) and, ultimately, the courts.

> I think this makes it clear that the MS-PL is fully compatible with (a
> phrase that seems more sensible to use here than "compliant with")
> other permissive licenses such as the BSD and MIT licenses, and that
> this was intended, not accidental.

I agree that the licensing would make more sense if "compatible with"  
were used instead of "complies with". But changing the wording also  
alters the meaning. Shouldn't we need analyze a license from the  
standpoint of what it actually says? There would be a significant  
distinction, as an example, between a license that is "compatible  
with" the GPL and one which "complies with" the GPL.

The wording of the MS-PL gives every indication that combined works  
need to "comply with" the MS-PL. Since BSD and MIT licenses do not  
provide patent indemnification, they do not "comply with" the MS-PL.  
If it were not for the MS-PL license demand that combined works must  
comply, they should be "compatible with" it -- but the fact of the  
matter is the MS-PL license demands compliance.

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