[ghaff]

>only to the ones with the NC clause

Which have significant problems. One of the smartest aspects of modern open source software licenses that's allowed them to become really widespread is that there's very little restriction by usage (e.g. only for educational use).

There have been attempts to better define NC in the context of Creative Commons probably going back a decade. But, in addition to the fact that it makes it a non-free license under OSI guidelines, it's really hard. The problem is that you either create hard and fast rules based on non-profits under US tax code or whatever (which allows some very large and potentially controversial orgs to use non-commercially) or you make essentially all non-trivial uses commercial. (Amazon referral links on your blog? Commercial.)

My personal belief is that CC should just eliminate ND and NC. ND prohibits remixing which was one of the rallying points around CC in the first place. And NC is essentially a feel good license that lets you be warm and fuzzy about contributing to the commons--while trying to make sure no one can make money from your work.