In the US there is a not small number of employers who take a very negative view of moonlighting. This is true in every industry, and in knowledge work industri

In the US there is a not small number of employers who take a very negative view of moonlighting. This is true in every industry, and in knowledge work industries like software it is compounded by a fear of IP theft. So whether it should be their business or not doesn't matter: they'll make it their business.