According to dev mailing list:
- Matcaps also made it in svn last week. Ton Roosendaal collects submissions for an extended set to include in default. Will involve the submitters for selecting a good set, and/or post it in public for a review.
Show off your Matcaps, maybe someone will like it enough to include it, and even if not someone else will find it useful.
CC0 assets are the most flexible. Less restrictions means more people will use them.