The namespace names for the page and index namespaces need to be in ProofreadPage.namespaces.php, not in VariantSettings.php (currently at line 3902 onwards). I would submit patches for this myself, but I have a new computer and haven't set up Git yet.
I believe this should be fixed before content can be imported, to avoid namespace problems akin to the ones we had with napwikisource.
(Semi-unrelated note: Why doesn't the hiwikisource settings in VariantSettings.php have the + in front of hiwikisource, like all other projects do?)