Complex sentence: Extensions run on Wikimedia wikis will be transferred to Git immediately after the core MediaWiki code, which non-WMF extensions in the shared Wikimedia.org SVN repository can either take up the offer of a transfer, or select to sort out their own hosting arrangements.
Split into simpler sentences: Extensions run on Wikimedia wikis will be transferred to Git immediately after the core MediaWiki code. Non-WMF extensions in the shared Wikimedia.org SVN repository can either take up the offer of a transfer, or elect to sort out their own hosting arrangements.