I would add that if you make a competing product to Microsoft, and they find out that you looked at their source code, they might use that as justification to o

I would add that if you make a competing product to Microsoft, and they find out that you looked at their source code, they might use that as justification to open up a lawsuit to check if you copied their code at all. Or if they open a lawsuit to see if you copied code, the fact that you looked might be used against you. IANAL so I could be wrong...