This is also the case with Ember, built by contributors from corporations actually using Ember in production. It's not just Angular, many libraries seem to be

This is also the case with Ember, built by contributors from corporations actually using Ember in production. It's not just Angular, many libraries seem to be written by people without a significant investment in their own library. It might be to promote their own education material, their personal brand, or just for fun. That's fine of course, but the projects will probably not be as stable.