Visual Studio's express editions certainly are allowed to be used in commercial projects.
Were they always? Because someone here claimed they weren't.
Yes, since their introduction. You own what you create and can use it however you want.
More info:
The DreamSpark and Academic licenses do have some restrictions. You still own everything you create, but their license forbids using those tools to build commercial software. Their intent is to get you comfortable with the tools used in the marketplace, not as an alternative purchase path for commercial users. Of course, the rules are not vigorously enforced and they can be easily overcome by downloading the other free tools from Microsoft and using them when the product is sufficiently advanced, transitioning from an educational experiment into a commercial product.