blender build bot what is the version "vs 2012" (since most is python ??)

Coding Beginning Blender Code and Development
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i am using the http://builder.blender.org/download/
i just noted the vs 2012 to some blender versions, for what is it used since most is python ?, is it now iron python ??

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Visual Studio 2012
http://lists.blender.org/pipermail/bf-committers/2013-June/040880.html
http://comments.gmane.org/gmane.comp.video.blender.devel/39674