Why Microsoft can't ship open source code

I've suggested a few times that Microsoft could go beyond just cooperating with the open source community and actually ship open source code. For instance, Paint.NET is a great alternative to MS Paint, so not just bundle it? Tonight I had a very long conversation with someone who is in a position to really understand both Microsoft and open source. Now I understand why my suggestion - though well intentioned - was hopelessly naive.

The problem boils down to code pedigree, the nightmare scenario, and software patents.

Why Microsoft can't ship open source code.