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

[Tzeng, Nigel H.]

>From: Donovan Hawkins [hawkins at cephira.com]
>>On Fri, 17 Apr 2009, Matthew Flaschen wrote:

>> 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".

>The permission that MS-PL attempts to preserve is permission to release
>under a closed source license. This is only preserved if the downstream
>project is open source...closed source projects certainly don't pass that
>permission on. If this is considered "partially" copyleft then the BSDL is
>equally effective at preserving the more common copyleft permission of
>releasing under an open source license. That permission is preserved under
>exactly the same conditions: only when the downstream project is open
>source.

>It's difficult to see the MS-PL as a hybrid in any meaningful sense when
>one half effectly destroys the significance of the other half. It's
>permissive, but only if you use the type of license they allow (closed
>source). And it's copyleft, but with an exception you could drive a
>permissive license through. Still, it does pass the license proliferation
>test: it is unique in combining the most restrictive license terms
>available for open source with the most permissive license terms available
>for closed source.

MS-PL ensures that anyone can use your work, big or small, competitor or ally, closed or open.  The significant difference from BSD/MIT style licenses is that they prevent other ideologies from removing that ability by creating a GPL fork.  

>From an open source project perspective this may be important to some folks because a closed source fork takes your code and that's pretty much the limit of the impact on your project.  Closed source communities are user rather than developer oriented.  If you're of the permissive mindset anyway then it works as intended.  However a GPL fork will take your code and potentially can take your community (your dev base) and create a new commons based on your work that you can't reuse without adopting their ideology.  This is seriously less cool and fortunately really really rare because for open source projects the community is your lifeblood.

Is this enough to justify the annoyance of a copyleft?  Personally, probably not, as I said it's pretty rare and we're largely a polite bunch.  But I can see how it would be attractive to some folks.

You can agree or disagree with the desire but it doesn't mean that the copyleft aspect has no significance.  

>From a FSF perspective, they're pretty lucky that it's a license associated with Microsoft and not a more neutral one.  The folks that might be inclined to take such defensive action probably dislike Microsoft more and would never use a license named MS-PL.  Now that MS-PL exists, the OSI is not likely to approve another permissive copyleft so the damage is pretty much limited to the MS open source ecosystem.