Microsoft released a tool called Microsoft Source Analyzer, or StyleCop. It analyzes source code for standards violations. It's a 1.0 release, so it doesn't do some things ... like have a published API for custom rules or MSBuild integration. So the community dug in and figured out how to do these things and now MS is firing off license-violation emails. Don't they get it? The community wants to use the product, but it's too limited ... these extensions help make it better.