This letter isn't a demand, legal or otherwise. It's a collection of requests that along with arguments based on a shared interest in the health of the ecosyste

This letter isn't a demand, legal or otherwise. It's a collection of requests that along with arguments based on a shared interest in the health of the ecosystem. You do realize that people do things or avoid doing things for reasons other than complying with the law right? This is one of those times. The only place where GPL comes into it is that it makes sure that goodwill requests is such as this one are as far as it will go and distributions can't be legally forced to comply. That lack of legal force makes it more important to have a strong community to keep the ecosystem healthy. So instead of ranting about "gah, they just don't understand GPL", it makes more sense to discuss the underlying problem, both on the technical side of how theming is implemented and on the cultural side of how default theming is explained and enabled.