I’m sure this exists in other places, but this is a neat explanation of how Xubuntu fits into the Ubuntu hierarchy:
As an official derivative, the
[CD] images are hosted on Canonical servers, Ubuntu developers will
assist the developers of Xubuntu when time allows, etc. However, as an
unsupported derivative, Xubuntu is entirely voluntary.
Given how little official support Xubuntu seems to receive, it’s amazing it’s such a nice distribution.