We have put the easyRdf library into gerrit, so it is available for deploy in production as a submodule in Wikibase.
https://gerrit.wikimedia.org/r/gitweb?p=mediawiki/extensions/Wikibase/easyrd...
When you pull latest master, you probably should update the submodule.
It might be necessary to delete the contents of the /contrib/easyRdf folder and do git submodule init (update) and git submodule sync (to clean references to the github remote)
Cheers, Katie