Microsoft is not going to allow GPL onto their phones.
Microsoft Bans Some Open Source Licenses from WP7 Marketplace

Microsoft has stated that its Windows Phone 7 marketplace will reject any apps that use the GPL (GNU General Public License) and similar licenses.

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“The Windows Phone Marketplace supports several open source licenses, including BSD, MIT, Apache Software License 2.0, MS-PL and other similar permissive licenses.  We revise our Application Provider Agreement from time to time based on customer and developer feedback, and we are exploring the possibility of modifying it to accommodate additional open source-based applications in upcoming revisions.”

Microsoft is doing the right thing and cannot be blamed in the slightest. The GPL is often termed a viral license and for good reason. Once you use it in your code everything is infected by it. Others say it is a spiderweb license, that once you are in the spider’s web, you can’t get out. The BSD license instead of the GPL is probably the single biggest reason to use FreeBSD over Linux, especially for enterprise business such as Microsoft, Apple, and others.

I don’t like the entrapment of the GPL. Students often first encounter the GPL in college, where they hear that the GPL is free and start using it. Only later do they realize they are trapped. Some don’t mind, wish they would have understood the license better.

Here is a simple rhyme to remember which license to use:

If you want your software to really be free,
    license it with BSD.
If you want your software to be in license hell,
    use the GPL.

This post shows that Microsoft feels the same as many of us who are anti-GPL.

Obviously they don’t want to have those who write their apps ever accidental depend on another app, only to find out the app they depended on is GPL, so their entire work must be GPL as well. They are doing what humanity tries to do with any virus, eradicating it and prevent infection by eliminating the virus, just as we have done with small pox, from the world.

For more information on the differences between the BSD License and the GPL, read this post.
Differences between the BSD/FreeBSD Copyrights and the GNU Public License (GPL)