> Just wondering - why isn't this part of mediawiki.org?
Most of the Wikibase components have nothing to do with MediaWiki. Having it on MediaWiki.org would make the whole software appear to be MediaWiki specific, and thus scare non-MediaWiki users away. Furthermore, it's sub optimal to have a collection of pages about a single topic on a wiki about something else like that, since the main navigation menus point to unrelated content.